Nobody ever said that being gay is 'normal'. What most liberals believe is that people should live without fear of prejudice. "Live and let live".
Children should be educated to life's realities.
According you people like you, heterosexual men should only find out about homosexuality by asking their new girlfriend why her adam's apple is so large.
Teaching about homosexuality not only promotes the acceptance of other people's sexuality without prejudice, but also serves to warn heterosexuals that these people exist.
For example:
Back in the 1970s I went into Manhattan with 2 friends of mine. We walked by a gay bar, which my friends didn't realize was a gay bar. They wanted to go in and have a drink. I refused. When we moved away from the bar, I told them that it was a gay bar. They couldn't believe it. They insisted on walking back and taking a look. Then they started acting like jack asses, yelling insults into the doorway. We were lucky we didn't get beaten up.
That's why heterosexuals need to be educated about homosexuality.