He said he's felt lately that I don't really understand what he is going through and that she has a past similar to his own.

Sounds like an excuse but maybe for the best anyway.

I really think that it would be good for him to see a therapist of some sort, and I have mentioned this to him. But ultimately, it has to be his choice

Yeah. You have to want to address it otherwise it will likely be just a waste of time. But another possibility could be a local survivor's group if there is one. Then there is MaleSurvivor.org but like any option he has to want to do something about it.

Other than his experience has he done any reading on CSA? Initially we often don't understand much about what we are dealing with ourselves.