Some points to be made.
First, there is no real equivalence between being "Affirming" and having an equal marriage policy. My congregation is not "Affirming" but has a completely open & equal marriage policy. (I'll concede that there's probably a logical equivalence between not being "Affirming" and not having an "open marriage" policy.)
Second, not all LGBTQ people want to be in "Affirming" congregations. We have a few LGBTQ folk in our congregation even though we have a neighbouring UCCan congregation that is "Affirming" that's literally a 10 minute drive from us. I've come to know one couple quite well. They've told me that they're at our church because they don't want to feel as if they're "the reason" for the church's existence; as if they're the church's "mission project." (That's the way one of the women put it.) They just want to be a part of the church family, and they feel like they're a part of our church family, and they are a part of our church family.
Third, "Affirm" requires a 75% vote to join. I have real problems with that. Unless you get a virtually 100% buy-in you have a problem and probably shouldn't take the vote in the first place, because all it's going to do is highlight divisions. Taking a vote and having it passed by 75-25? I'm not sure I'd feel really affirmed if a quarter of the congregation essentially said "we don't want to be affirming to you."