The lack of viewpoint diversity and the suppression of free speech at many American universities is a growing problem as some of the above commenters have observed.
There is a groundswell of committed professionals that are trying to reverse this unhealthy trend. The other day I was directed by a colleague to this website created by some of these people:
Here is a snippet from their welcome page:
We are a politically diverse group of social scientists, natural scientists, humanists, and other scholars who want to improve our academic disciplines and universities.
We share a concern about a growing problem: the loss or lack of “viewpoint diversity.” When nearly everyone in a field shares the same political orientation, certain ideas become orthodoxy, dissent is discouraged, and errors can go unchallenged.
To reverse this process, we have come together to advocate for a more intellectually diverse and heterodox academy.