I think I've already explained the piece about exclusion in the example about the young gay guy.
Regarding offence, its in the eye of the beholder.
Say I was on a train with my mate and a couple of pissed up lads got on and started having a go at the asian family sitting opposite. Perhaps we could see the father felt humiliated but didn't want to do anything to make it worse and possibly endanger his kids. I'd be really offended by their behavior and I hope we would have the courage to ask the lads to desist. The lads would probably take offence at us telling them what to do and start on us. we would then have to offend them further, in fact we would probably offend the s**t out of them leaving them with a considerable amount of dental work.