You would be very surprised. VEERY surprised. Just Goggle the gay marriage debate here in the United States and you will find out PLENTY of people wouldn't bat an eyelash at it.
Then I'm glad I don't live in the US I guess.
If I heard something like that said to a kid, I'd get a bad case of pitch black anger.
I would think the teacher said "Not normal" because it's just a common thing majority is heterosexual. It's a matter of fact that if we were all homos, the world would be wiped out immediately due to the extinction of human race. On the other hand, homosexuals have been acknowledged throughout history (even by God). How should I put this... I used to be prejudice because I thought it was a sin, we would be outcast by our own family, society, we will all be condemned to hell but as I get older, I realised a relationship is not about the gender of the other party, rather it's about how much we love that person. Of course, we should also respect whether the person in question reciprocates our love intentions or not as he/she may not be interested in same gender relationship. So, when XXX told her friend that she likes her (but XXX was rejected), I didn't find sad. I however did find it very disappointing when her friend (that used to be close to her), distanced herself and treated XXX like a disease. Why should you be disgusted when you have been loved?
As for the sinning bit, don't worry, everyone sin everyday. We live by God's grace (^_^) and He loves us (period)...I think it's the family and society that we seek acceptance from. It always hit hard in the heart when heterosexual do not acknowledge homosexuals. Oh my goodness, why are we even putting people in categories to start with? Leave science out and we are ALL just "normal" human beings born to love another human being. We get angry (and sometimes violent) at people for disliking us - perhaps as a form of demand for acceptance. But don't you think that is also being prejudice towards them?
To each and everyone their own tastebuds/ likes/ dislikes. I don't think we should flash out "respect gay people" propaganda... rather, "respect my choice".