Well, the offensiveness is always there. If you'd had an accident confining you to a wheelchair for life, and then the day after being discharged you were sitting in your wheelchair watching the snooker and one of the commentators said, "well, Jim, even a quadriplegic could have potted that", you'd be offended.
Having said all that, the question is whether the right to insult people exists or should exist. It's a question that was skirted round when the whole Arab world suddenly went off Apple Danishes, but even then wasn't properly addressed. Do people have a right to go through their entire life without ever being insulted?
I would say, "no". For several reasons.
1. Insults are important linguistic tools, and the genuine art form of insulting someone in an original and witty manner seems to have been in decline since Wilde;
2. Learning to take an insult greatly aids personal pyschological development, with the alternative being a society that cries and sues over the slightest little thing;
3. If people and society in general become more immune to insults and verbal abuse, through allowing them to proliferate, perhaps we can get worked up about the important things instead. Like murder, rape, torture, hunger and disease.
So roll on insulting behaviour! Bring it on, I say.