A couple things I think you’re missing:

Your assumption that one of the positions, either liberal or conservative, must be correct, is wrong.

Second, the assumption that professors know better than the general population in all cases is also incorrect. People in academia have a way of thinking that is sometimes divorced from reality and real world experience. Professors can be much more wrong than the general population in some cases.

This highlights the original point: viewpoint diversity and rigorous debate are the best tools for discovering truth. If your idea is so fragile it can’t exist outside of some protected ecosystem, the idea probably isn’t very good to begin with.