I find a lot of things offensive, but most I can weather without loosing my cool. I only get into "HOW DARE YOU" territory when the severity of something is so great that I can't not be offended.
For example: douchey guy says something disparaging of women like they're too emotional and can't handle the stress of blah blah blah. Annoying, stupid, and offensive? Yes. But I've heard that and have snappy comebacks and good arguments I can use. However, if said douchey guy happens to be with a girlfriend and proceeds to do something douchey and controlling or whatever I'll have to say something and call him out.
So, basically, when disrespect goes from words and opinions into actions I'll get all how-dare-you on someone.