The reason I would expect is that they think the teachers are showing their kids explicit sexual content, encouraging them to be transgender, and telling them about how they should hate America and white people. Is that not accurate?
Bait aside, nobody calls you homophobic for asking good faith questions about how the schools budget is spent. But it would be absurd to imply the 12 hours a year kids are taught about sexuality is somehow derailing the entire curriculum. When talking about revamping education, only people that have fully drank Kool aid would think "it's because all of that money is used to turn my kids gay".