I would step back and try to put this in perspective. For some people who've been through a traumatic event, any mention of those events without the utmost sensitivity is offensive. There's just too much pain associated with the memories.

But for somebody who's never experienced that event, would not be prone to doing those things, and has no connection whatsoever to the topic; there is no similar frame of reference. For them a joke is a joke and nothing more. Many people who have been through terrible events and have processed it can also find the humor without it triggering them. Or they use humor to cope.

So he might be on your side about domestic violence in general. But we all bring different life experiences to the table and different ways of coping with those experiences. You can talk it out with him if you are both the 'talking it out' types, to find where your differences are and maybe develop some empathy and understanding. However, it might just be something you have to accept in him and something he has to accept in you. If things are otherwise good, I wouldn't let a difference of opinion about comedy get in the way.