Colleges and universities are supposed to be centers for the free exchange of ideas. In the U.S., many have become centers for sorting ideas into two bins. The approved ideas are inculcated; the disapproved ideas are censored.
There’s no indication that Howell did anything other than express an opinion. According to the Facebook page Save Dr. Ken, “His teaching what the Catholic Church teaches in a course on Catholicism was deemed to violate University rules of inclusivity…”
I can't say whether I agree or disagree with Howell, because it's not something I've given much thought. But I don't know how a university can have "rules of inclusivity" concerning opinions. (Actually, I do know how: by applying them selectively.)
It turns out that Howell is popular among students—and not just Catholic students. Even the student group Atheists, Agnostics & Freethinkers has rallied to his side. (I think it’s a safe bet that they aren’t defending his opinion—just his right to express it.) Howell apparently has a reputation for promoting open, honest, and civil debate. And that’s exactly the sort of thing that’s supposed to take place at universities.