It’s perfectly fine to criticize or challenge the beliefs of another – especially from the pulpit, when it’s a moral issue. I’ll defend the LGBT activist as staunchly as the Christian or even the Muslim in that regard. There is nothing in that exercise that imposes anything on anyone. It may make the other side uncomfortable, but that’s too bad. One person’s discomfort does not trump another person’s rights in America.
It’s another story entirely when the power of the state (i.e. any government) is used to intimidate or persecute that protected speech. It was/is wrong and evil when so-called Christians do it. It is wrong and evil when the mayor of Houston does it.