Alright so first off if you were to start with the problem of evil, which is basically the backbone of the amputee argument, at least it seems. To say that you believe in evil, you are assuming a moral law to know what is good or evil, and to have a moral law means that there must be a moral law giver.
I am going to disagree a bit with some of my fellow atheists and argue that there is objective morality, at least within certain resolution limits. My reasoning goes like this: human beings are entities of a specific nature. There are certain things that are genuinely harmful to human beings, like causing them injury, raping them, stealing from them, enslaving them, and so on. There is general agreement among societies that doing such things to someone is "bad" and doing certain other things (treating people with courtesy, listening to what they have to say, respecting their rights to life, liberty, and the pursuit of happiness and so on) are "good"--when applied to people recognized as "Us." Moral differences in societies in this sphere generally arise from where the boundary of "Us" is defined. To my knowledge, the rules of moral treatment are fairly consistent throughout history, when you're talking about male landowners. Women, children, foreigners, etc. have often been defined as outside of the boundary of "Us," so the way they have been treated has varied widely. Moral progress happens when the boundary of "Us" is extended to include more and more different types of people, and to some degree at least, the planetary biosphere on which we depend.
The type of morality I'm talking about here is your basic Bill and Ted morality ("Be excellent to each other!" *air guitar*). When we get into things like consensual sex (what type of partners, sex positions, kinks, etc. are OK, which ones aren't), what foods we "should" and "should not" eat, whether we ought to wear clothes made from blended fibers or not, which mind-altering substances we can use and the like, "morality" does become a great deal more subjective and diverse across different cultures. However, to the extent that we're talking about demonstrably objective morality
this derives not from some "moral law" or "moral lawgiver" but from principles
derived from human nature and our need to live together in cooperating societies.
But OK, what if all morality did
derive solely from the authority of a "moral lawgiver (MLG)?" If the MLG has no boss of its own, then for the MLG there is no such thing as morality
. How can there be, when the MLG doesn't have an MLG? Which means, in turn, that whatever "moral laws" it issues are wholly arbitrary.
We see this exemplified in the Bible, when Yahweh gives Moses a "Commandment" forbidding killing (which was supposedly given much earlier, to Noah), yet the moment Moses comes down from the mountain, he and his Levite stormtroopers kill 3,000 people for having a pagan religious celebration in his absence. This "Great Lawgiver" goes on to order his people to exterminate entire societies and take their land, presumably relaying the orders from Yahweh himself. Also, according to Biblical situation ethics, it can be OK to rape little girls after murdering their families in front of their eyes (Numbers 31:17-18). So, the only thing that's keeping you and people like you from murdering your own children is that you don't hear the Big Booming Voicetm
of your Moral Lawgiver telling you that doing so is the new Good. Right? See: Yates, Andrea.
Another problem of the authoritarian "morality" you propose is that "law" is only as good as its enforcement. If a government had a law against the use of LSD, but never, ever enforced it even if there were psychedelic churches handing it out on their communion wafers and broadcasting the whole thing on their television ministries, then for all practical intents and purposes, LSD is legal there. In the same way, if Yahweh has a "moral" law, but never, ever does anything to enforce it (as is the case), then his moral law is non-existent for all practical intents and purposes. Threats of burning in Hell, or ambiguously ordinary natural events (Yahweh sent Katrina because he doesn't like buttsex!) don't count even if true precisely because the existence of the MLG, the "laws," and the connection between them is...wait for it...subjective
. A preacher can interpret Katrina as punishment for buttsex, and a Druid can interpret it as punishment for too many people driving cars. Who is right? Can't tell from any observation of the hurricane. It might also be just a bad storm. Returning to my analogy of the "law" against LSD: let's say there was no actual law written on any law books published by the government. Instead, there were a few people who claimed that the law was passed in a secret session of the legislature, and that the incidence of car accidents and bank robberies involving dead hostages were actually the result of government covert operations teams "enforcing" the "law" against LSD. There is still no actual, objective law. The linkage of those random-appearing events to a "law" that may or may not have actually been enacted by the government is a purely subjective
In the same way, different Bible-believers (Christians and Jews) have different, subjective interpretations of what Yahweh's "moral law" is. So that sort of "moral law" does not provide firm moral absolutes. It provides the very sort of whimsical, arbitrary, subjective "morality" that you're trying to argue against.
Bonus Question: what if you found out that there was no Moral Law handed down from the heavens, that nothing is forbidden and everything is permissible. Would you act differently?