Why take offence? Why get angry? Nothing good would come out of it. Clearly it doesn't make you any happier, except comparatively when you drag someone else into the fight.
Yeah, so someone can't keep his mouth shut, or pass things through their brains before speaking. Yeah, so some people just have malice in their blood. So? It's not like we have much control over what others can or can't say. Let other people be other people. What we can control is ourselves, so let's do that.
The simplest method is distancing. Don't make yourself a participant. Better yet, treat the part of you that does feel offended as a subject of study. Look upon him and wonder, why does he feel offended? Is there any good reason, or none at all? Laugh at him, even. Cordon the negativity off.
Otherwise, just take a big stick and whack the hell out of your foe. There's no room for half-measures!