All in all, it's pretty hard to offend me. I've long since given up being 'offended' on other people's behalf, and that's probably over 90% of the 'politically correct' offense taken. I think 'offense' is learned, or more accurately, contagious. People witness a strong social reaction, and it sinks right into their subconscious, and they don't even remember the event, but they remember on a 'gut' level, 'Be Offended IF...'.
But being slow to pick up and internalize such social cues myself, I am a bit more immune to these contagions than most... normally functioning people. I can look at them from the outside in. Since most of my 'social' behavior is emulated, rather than natural, it's probably easier for me to cull stupid, emotional 'reactions' to things.
I believe the evolution of what is 'offensive' operates on misunderstanding the cues that caused social outrage, then passing on the new, modified 'outrage' triggers.
There are evolved social 'qualifications' for telling a joke...
It helps if you're obviously
disabled, if you're going to make jokes about being disabled.
If you're black, you can apparently say 'nigger' all you like. Obviously a white guy can't, unless he's got a hood and/or swastika on him.
If you're jewish, you can tell 'antisemetic' and even 'holocaust' jokes. Basically, same as above, if you're not.
If you're asian, you can joke about all your family looking alike. In some cases, if you're not Asian (especially black, for some reason), and you can't tell a Japanese from a Korean from Chinese (and various groups within China) at a glance, look the fuck out.
Folks from different places in South America get all kinds of tweaked if you misidentify them as Mexican. And naturalized hispanics tend to hate the various flavors of 'illegals' (legal or not), mostly for the stigma and backlash that they get from the mess.
Basically, the 'offense' in some of these cases kind of spits in the eye of the 'I have a dream' speech.
"I have a dream that my four little children will one day live in a nation where they will not be judged by the color of their skin but by the content of their character."http://www.americanrhetoric.com/speeches/mlkihaveadream.htm
Which is a perfectly good response if someone gets all butt-hurt that you thought they were 'Japanese', 'cuz nobody passed on the memo to you to call every Asian 'Asian', just to be safe.
Remember the fun when some people claimed Obama wasn't 'black'?http://www.colbertnation.com/the-colbert-report-videos/81955/february-08-2007/debra-dickerson