It's not about forcing anything on a kid. Furthermore, these lifestyles aren't normal. There's nothing wrong with being not normal. Failing to educate kids does risk the entrance of hatred and fear. Additionally it is very possible to disapprove a lifestyle and yet educate a person on the sanctity of personal freedoms/choices.
That's exactly what they're doing (using force). Unless a parent can afford to put the kid in private school or home school the kid, both the kid and the parent have no choice in this matter.
I haven't seen the curriculum, but I would be floored if it didn't treat all of these lifestyle practices as "normal." There is something wrong with compulsory education that teaches a kid that abnormal behavior is normal.
I don't buy that "hatred and fear" argument. It's a total overstatement. Like saying that all people who don't approve of these varying lifestyle choices are "bigots."
We are all already taught to respect people. We have laws on the books that protect everyone, regardless of what kind of lifestyle they lead. I view this as similar to unnecessary "hate crimes" legislation. We already criminalize assault, murder, etc.
This really is about trying to force-feed an agenda to the public and normalize abnormality. But at the end of the day, the primary issue for me is the intrusion on the parents' rights.