As a non-Christian with life-long experience in a Southern Baptist region, I would say that the answer to this question is heavily denomination-based, and possibly regional.
Discussing religion and social mores on the internets was a revelation to me (no pun intended ;)), in as much as I quickly learned that what I had grown up with as standard Christian practice is not, in fact, universal to all denominations and regions.
IME, yes, Southern Baptists preach that we are all sinners, but in reality, some sinners are more sinful than others. The SB church frowns on divorce, extramarital affairs, fornication, and so forth - but don’t generally shun those who participate, even when in an ongoing situation.
However, some sins are near-unforgivable and will result in shunning. Homosexuality is one of those, unless the gay person is willing to commit whatever symbolic self-flagellation is deemed appropriate to show their repentance.
This is changing, but very, very, very slowly.
Obviously YMMV, but if you are dealing with an SB congregation, I doubt that you’re imagining the double-standard. It’s certainly not a standard Christian doctrine, as many other denominations handle things differently.