There are several things in play I noticed in my own response. I often let something offensive slide and will continue trying to get my points across in this or subsequent posts. My underlying thought is to help the other person, or understand them. That in a way, is a submittal response, not a strong one. The insults fly over my head unless it's blatant. Sometimes that may be useful... I'm good at finding others views. Sometimes it's not good, dishonoring myself, while not pushing back... the other isn't going to change.
I know I take insults because as a kid, I took lots of insults and felt no means to fight back, so I just accept them. Conditioning.
I'm not saying there is a right or wrong response, just an observation of you... and are you ok with you?
I think... it's right to call people out on their insulting... tell them when they are out of line.