Freedom of speech is the first amendment, and even though it is counter intuitive, criticizing america, it’s institutions, and especially capitalism is fundamentally american speech - quite possibly the most american thing you could possibly do in the eyes of the founders.
Colleges of sciences and engineering rarely would have lecturers venture down that road anyway, except in courses about society, history, and philosophy embedded in those schools, so I don’t think it’s a problem in any case, and your characterizations are being overblown.
Other research areas will be inherently fuzzy on that. That’s almost tautological - the people teaching history, philosophy etc… are going to have an opinion because they wouldn’t even be teaching unless they were passionate about the field.