I want to enlist to "the more I see this sensei..." team.
The guy is shit not because he does what he want. It's because he doesn't put himself in other people's shoes, doesn't know and care what other people want.
It would be okay to take "we break up when it's no more fun" stand with a girl of his own age and similar love experience (and he even has decent chances of getting the girl same as him), and visit love hotels as much as you want then. And in this case it's natural to not care about partner's past and future. I'd rather say, it's the only possible way of such relationship to exist. But not everyone is like that, luckily.
I admit that I belong to other type of people than him, and my antipathy to him comes from that. In highschool I was wondering, why people start to date so early. One of answers was "to have sex fun..." And from the tone I figured "...as long as it goes". Being a type of "start to date only with potential life partner" (along with not meeting a soulmate because I'm a shut-in) is a reason I never dated anyone, though I'm pretty sure I could have my share of fun. I just don't want it this way.
I like how it's shown that Meguro-san doesn't like sensei's ideas, and how she likes Koga's. The only thing I don't like is how she still accepts sensei's statements. She is too naive to accept it all, he is too naive to teach an innocent girl such things. He is harmful because he doesn't realize that he harms people of another type, that's the most annoying.