Luke begins seeing a new man and it's someone Ben doesn't trust or like. He isn't sure why the thought of Luke with this person makes him so angry, but it does and he isn't shy about expressing it.

Ben's anger could be completely justified, maybe this guy IS a complete loser.
Or it could be based on something irrational, maybe the guy is from a different humanoid species and Ben (in true Empire/First Order fashion) finds the thought of that distasteful.

I just want Luke to get some and for Ben to be raging about it. Maybe it even jealous and turned on depending how mixed up his feelings are.