You are right, it seems tolerance is a one-way street with that guy. He wants people to be tolerant of homosexuality, but anyone with a different orientation to him is a loser. And I agree that sexual relationships between teachers and their own students is extremely unprofessional, even though it is not illegal or immoral.
What always annoys me is how some do-gooder pretend conservative laowai in China frown upon any sexual relationship between a teacher and a student. For example, a 22 year old Chinese student is an adult and she has freedom of choice, and should have a sense of responsibility. The fact of the matter is that younger women and older men often fall in love with each other, eg, 45 y/o man and twenty-something woman.

However the Huizhou poster would call these men "losers". I remember he was also very anti-prostitution, would frown upon pink room girls and their clients, so much for tolerance!

I often find that the do-gooder conservative types are the ones with the most skeletons in the closet, who are really trying hard to hide something.