Now I truly understand what could make people mad. The hard part is working around and getting something selfish out of the person I'm directing my attention to. I guess there has to be some elements set up such as peer pressure, timing, and the setting. If it's done at a place where you could look like the bad guy then it's probably better not to engage in the conversation unless you're considering it to be your last stand or something.
I think over all it's just feeling the proper vibe and going for it. The way I see it is that it takes a lot of preparation like studying for a test. You have to think about every possible outcome and make sure those possibilities won't ever occur. You also need a proper motive and probably a sensible pretext if it sounds really offensive to the person.