Well, you do have a point. I guess there are two kinds of offensive (at least): things that offend you personally i.e. things at which you take umbrage, and behaviors that we consider offensive, in the abstract. For instance, I think most of us could agree that dropping garbage where you stand is offensive. (especially when where you stand is a few feet from a garbage can.) Saying racist or sexist or just generally ugly things to people is offensive – in a general, abstract way that I figure most people would agree with. Offensive behavior usually involves disregarding the basic rules of conduct that we all feel like we had down in kindergarten.
And I agree that we have probably fuzzied up the boundaries between “offensive” and “annoying.”
But my first response to the OP – about class attitudes – is something that really does offend me, personally. There aren’t very many things that I get that kind of offended about. Somehow it’s just a giant button for me when people assume, because of what they perceive to be my “class” (lower socio-economic status) that I am surely less intelligent, less wholesome, or less altruistic than they are. In fact, it occurs to me that I rant about this a lot here.
Must have been that sneetch book when I was little.