The "hate" is a little strong, people are just not interested in having male characters in agame with a full female cast, yeah, that's so weird.
And the fact that the vast majority voted for no males (I voted for optional personally), doesn't mean the vast majority is wrong, it means your opinion and tastes are part of a minority. That doesn't mean the majority is hateful either. (when I say you, I don't mean you personally)
What I don't understand though, is why make a poll if you don't stick by it. First, it shows that you (Su.IT) don't care about people's opinion, and second it also shows what your audience wants and expect from you, that's your market, that's where people who gives you money are (sure, most of the people here don't give you money, but I'm ready to bet high that most people that support you financially came from here).
Don't get me wrong, it's your game, you do whatever you want. But if you wanted to put male students in the game no matter what the poll's result, you shouldn't have bothered with the poll in the first place.
"Hey guys, I have an idea, what do you think? Not like me, huh? Well, I don't care, I'll do it anyway"
My personal opinion on the matter is that it doesn't matter if you introduce male students through modding or directly into the game, that's still new characters you will have to render and incorporate into your game. Game that already has a very slow development. 1year and half, and you made close to 0 progress with what you had initially planned. Do you really think adding side/optional content will speed up development?
I highly doubt it.
But that's just my opinion, and I'm not looking for a fight, you do you, that's your project, you're in charge, and I respect that. I can only wish you good luck.