I will never fully understand why anyone can think that "do-gooder" is in any way an insult.
It's very simple. Race, or religion, or gender, or sexual preference, have nothing to do with whether or not anyone is rude or inconsiderate. So to invoke such characteristics is to risk being labelled racist or sexist or whatever when you could have said "so-and-so was such a jerk by queue-jumping". That way you are guaranteed a) to be right, and b) not to lose yur job on the grounds of racial discrimination.
Furthermore, if you say something and then continue saying it when someone in earshot is clearly offended, you're also being insensitive and rude.