I don't think it's always SPAG, or at least, not always directly.
For example, I don't think Shirley Phelps' is suffering from SPAG. Fred Phelps on the other hand, I would say so. Shirley Phelps is indoctrinated, it's not her ideal of 'God' it's one embedded into her brain. I also think a person could potentially delude themselves from how they're reading the bible, if they took the bible that literally, then they may warp their views around it rather than the other way round. You might think of it as somebody who was a nice guy before but turning into somebody completely different as a result of religion. For example, you hear of cult worship.
In the case of the Nigerian witch burnings/killing, I could see a case for it to suggest that it's not SPAG but using a literal reading of them bible and having it fuel their superstitions. This idea that the cause of pestilence is witchcraft and then find somebody they think is a likely candidate and deal with them in a biblical manner.
But a lot of the time, I do think SPAG, because I think people often think in wishful thoughts and enjoy ideas about the universe that comforts them, or make sense to them in how they're able to perceive it or how they feel. It becomes less about how God is defined and more about a person's own perspective, and I think it's right, there isn't 38,000 version of Christians, sects, yes, but I think for everybody it's minutely different from the next guy in the sect before individual interpretations, variations in thought and personal feelings come into play - I suppose to that degree you could argue there is a level of SPAG in each believer; an individual's own expectations projected onto their deity. I think a big give away of SPAG is when somebody starts off with the phrase "I feel that God..." as opposed to "the bible says", though, the SPAGers who have put more thought into it will back up with the bible as well (see Fred Phelps), so I think it's harder to identify all SPAGers.
So SPAG is just having you own opinion about a theological concept.
Given the bible is meant to be the word of God and his command to the faithful, then there should be no opinions about a theological concept here, because it should be as God has stated it. These opinions can be born out of applying one's own ideals onto the concept and that is self-projection. The God of the bible ends up on taking the characteristics of the people who believe in him rather than the other way round. For example, you could have somebody say, "well, homosexuality is a sin, it says so in Leviticus", then try to find a way to reason out of any ideals in the bible they believe is wrong. I find it saddening
that when reading the bibles laws you'll end up reading the 10 commandments and people agreeing, "oh yes, there are good Christian values" then a few pages on in the same book (Deuteronomy, I might be wrong, but I know it's the same book) STILL talking about the laws of the bible, we come across their sexual laws. We have adultery - yes, yes, yes we must punish them, that's wrong, then rape - horribly wrong, we must punish them, sex before marriage? Yep, we believe that's a sin! Being a rape victim? We can't punish them. If the victim is in a town and does not scream, then the rapist should pay her father 50 silver and marry her.
I don't think that's having your own opinion about a theological concept, it is picking and choosing. You only live by the laws you like but ignore the ones you don't or trying to rationalise them when somebody picks you up on it. Similar things happen when the bible contradicts itself. This is why I make the argument that if you really wish to follow the bible word for word then you need a mind capable of multiple states at once, such as having a multiple-personality disorder.
Of course, there are those that actually try to do that.
I know there are other theological arguments surround God and the bible and that not everybody is a literalist, but to take a much more metaphorical approach itself requires a level of self projection, because you're dealing with something subjective and not concrete (figurative language is not concrete), you're working with what appeals to you, your interpretation is based on your own thoughts, experiences and ideals and not necessarily those intended by the author - sometimes it's impossible to know what was intended by the author because you cannot personally ask them. For example, we can't ask Shakespeare about his work because he's dead. This is why people tend to use the 'secret decoder ring' argument, nobody has a secret decoder rings and we can't decode exactly what is meant by anything claimed to be metaphorical. I think we can take out possibilities, but things like "it is easier for a camel to pass through the eye of a needle than a rich man to enter the kingdom of heaven" actually has multiple arguments on its meaning. I don't see any rich Christians seeing the 'needle' being the kind of needle you use in threadwork. Or to take the idea that it is impossible for rich men to enter the kingdom of heaven. Imagine Mitt Romney saying it in front of his millionaire investors.
Of course, I think there are things we can suggest are likely just based on historical context, but history in itself is something that's difficult to do with complete accuracy. There's a level of expectations, particularly created by things we already know and it's hard to account for any possible anomolies. At least, from my understanding of the subject.
But to drive back to point I was making about subjetivity and interpretations, Dee Snider argued in court over the lyrics of his music with the argument over lyrical interpretation, he suggested people project their own thoughts, expectations, experiences and ideas into the lyrics and make it their own. Where the critics were seeing sado-masochism, Dee Snider was writing about a throat operation (it's Twisted Sister, they don't take themselves seriously). Or the author (whose name has escaped me), whose son was given a bad mark on his essay about a book his dad wrote and even though he asked his dad what his intentions were, but the teacher completely disagreed with it. So how we see something might not have been how the author intended.
So having a more subjective (or metaphorical/literary) approach also gives room for SPAG. We project our own thoughts, expectations, experiences ande beliefs. Interesting, psychologists suggest we do the samething when it comes to memory, it's called 'Reconstructive memoryWiki
Then what about the philosophical approach? Ruling out empirical approaches to philosophy, because there's nothing empirical going on with philsophy surrounding the bible, because it's not dealing with the observable or the measureable. We've got the Teleological Argument, the Ontological Argument, the Cosmological Argument and various other a priori philosophical approaches. The kind of approach the like of Plato would use (and of course, he also had his own concept of God) - ones based on thought and not fact or even interpretations of fact. The arguments of Philosopher Thomas Aquinas on Natural Law was Christianifying Aristotle's philosophy. So, would this mean we're taking a much more logical or reasoned approach to understand God and the bible? Does this mean that we can treat the ideas of religion from the view of a reasoned 'opinion' rather than SPAG? Generally this kind of philosophy understands 'truth' to be found within logic, that the 'truth' can be found through thought and reason. It tries to make 'truth' something that's subjective. This of course is where epiricists see fault and of course, it's what scientists try to avoid.
This is exactly like the literary approach and opens much room for self projections because as logical as a person tries to make their argument or how they might view their argument to be based on a reasonable opinion based around logic and not self-projections and the amount of reason they try to use, at the end of the day it comes down to them. Each philosophical argument on the existence of God requires you to accept a certain version of God. The Cosmological Argument doesn't rely on what the bible says, it tries to be more compatible with science. The Teleological Argument does state direct from the bible, but tries to make God fit into reality, the same with the Ontological Argument. The Teleological argument requires the assumption that complex things MUST have been designed and can't be a result of causality, which is not actually a biblical claim. This has been projected onto God because the philosophers writing about it have been trying to make reality and God compatible and it is the bridge between the 2. A God who creates, we have no evidence, so lets make some logic we can apply to God to suggest why he's real and a creator.
It's about how they see the world, what feels right, what works within their own judgments, what makes sense and their own ideas, expectations and experiences. They may not only shape God based on this, but reality too. Thomas Aquinas projected his Aristolian views of reality into Christianity. Shaping Christianity around a philosophy rather than just relying on what the Christian texts actually say. Yes, in this regard it's not just himself he was projecting, but ideas he acquired from Aristotle's work (and others who wrote about Natural Law). I picked Tom because he was very influential and Natural Law is a view held by the Catholic Church. So, we can see how big of an influence one person's SPAG has had.
So SPAG can work itself in any number of ways for any number of reasons. I think impossible for somebody to have an 'opinion' of God that's not built around some level of self-projection. But not all versions of God are necessarily based on an individual's opinion or opinions they themselves have formed. Some are actually based on what the bible actually says, others are based on what's been feed to them and they're not used thoughts of their own.