Public schools changed my evangelical views through my twenties, making me doubt my faith and the values with which I was raised. My desire to homeschool was based partly on what was my personal experience there.
I didn’t become a Christian until I was in my 20’s, but I sure saw enough of what you’re referring to. That played a role in our decision to homeschool.
My two oldest are in secular college now and appear to be impervious to the brainwashing that can happen there.
Although, I don’t think that to this point they’ve had any vehemently rabid Christian hating socialists for teachers.
When they were still at home through their teen years, we discussed a lot of social and political issues and thought them through very carefully. They are decidedly pro-life for that and conservative on all political issues.
Knowing what you believe and WHY you believe it is good defense.