Everyone bashes the main character, but he's become someone who can stand his grounds for his beliefs. Instead of sleeping with any cute girls that approaches him, he takes the matters seriously and doesn't sleep with her just because he's horny, plus he turned her down in a manner that didn't make her feel disliked. If anything, this guy has his morals set straight, plus he told the truth to Mizuhara, which is another good thing to do, even if she didn't believe him.
I seriously can't understand why everyone hates the mc so much, he started out as a piece of shit but it was clear the goal was to make him grow up as the series went along, which is precisely what's happening. For someone who hired a rental girlfriend and vented his frustrations out on her because he felt dejected, being able to turn down someone he doesn't love so that on't hinder his relationship with the one he does is a very commendable act of integrity!