The college, as an arm of the state, can’t limit speech unless it fits in one of the narrow exceptions recognized under the First Amendment. “Ensuring a non-threatening environment” isn’t one of the exceptions. (Note: a private college could take more steps to limit speech.)
I’m not saying that all federal courts would agree with me, but that’s my interpretation of the law. As always, people love free speech until they encounter some speech they really don’t like, and then they look for creative ways to argue that it isn’t protected. Sometimes they succeed.