No, they don't just believe that homosexuality is wrong. They preach that everyone who is homosexual will be killed at Armageddon. They conceal (or are ignorant of) the fact that homosexuality is NOT a choice, plus it appears in the rest of of nature (500 species), thus is not "unnatural", so one cannot just "change" to being straight in order to avoid being toasted in Armageddon. That is the definition of homophobic speech.
Of course, they answer that a homosexual could avoid being roasted in big A, as long as he doesn't practice homosexuality; which is like telling a straight that he must remain celibate all his life to avoid being executed. This is the definition of oppression.
So, we have homophobia plus oppression. If speaking against homophobia (and other forms of racism and hate speech) and oppression is "stigmatization" and "frowning upon", well...