I meant to thumbs up, I completely agree with you. Misogyny and rape culture are pretty prominent in most yaoi :/
If he was homophobic then he wouldn't be hang out with Umi and what he said about Umi is true because Umi would just sleep with anyone who was kind towards him. And he never slap Umi. I do agree that he has a harsh mouth and I also don't like the fact that he is judgemental since I think that no one has the right to judge.
So now that a few more chapters have come out since then, I'm revising my opinion. His apology also went a long way, and I'm looking forward to the both of them coming to terms with their issues. :P
Like IOTR said. I suggest you keep reading to watch them grow. It gets better.
I was having a hard time getting into this because senpai's whole slut-shaming, homophobic, moralistic hangups were just too much. I get that he had a deadbeat dad, but that's no excuse for going around pushing your judgment onto other people.. When he slapped Umi and said "You brought this on yourself" (rape culture, much?) I kind of just gave up on him.