For context without the hysteria - Cruz proposed an amendment allowing parents to fund a 529 for K-12 education.

At face value, it sounds OK. Kids incur costs, having a tax-free vehicle for them is good.

However, as Sen. Wyden pointed out - funding for K-12 education advocates spending on non-public education, aka parochial/private schools. If the US Gov't is incentivizing people to go to non-public schools (aka not held to certain standards regarding their lessons), this raises a big concern about what the students are being taught. Aka not support the theory of evolution, etc.

It may seem like a stretch, but it's fairly direct when you consider their actual goals