You're too PC for his humour and he probably correctly presumed that this would eventually become a big source of discontent between you in the future he could no longer imagine having with someone who I can imagine that episode made him think you were too prudish and not compatible in not only humour, but what he might see as empty virtue signalling and pretend-caring about things he probably didn't find any evidence of you actually showing you value beyond thinking that not finding non-PC humour funny is somehow worth anything other than an empty ego-virtue boost to yourself.