To be clear, it is about the effects of certain churches and kinds of churches. You cannot issue a blanket condemnation of "churches" when there are so many churches who do not fit the model and are working to fix the problem.
So, the real question becomes "What can those churches that are already in support of LGBT do?"
Be open and welcoming to those gay kids and adults who need a church home and have to leave the one they are in. Don't just wait for them to come but get out there and say, "Come on in, we want you here!"
Speak out loudly in support of political and social action on the issues, Don't be afraid to say that we are church-going, Bible (or whatever) believing Christians (or whatever) who believe in protecting LGBT from discrimination, who believe in the right of all to marry, who believe in the right of all to live as they are born without shame, fear, or pain caused by religious beliefs. Fight for separation of church and state that includes legislation based on rights for all persons without exceptions based on faith.
Be visible in their support of LGBT and other minorities so people can see which churches are "safe". Whose churches marched in, and had official representation at, their local Pride celebrations and parades? To say "we are welcoming" internally but be so quiet about it publicly that no one can find you is meaningless.
There is probably more, but those should get things started.
(Yes, we UUs try to do all three. I'm sure we aren't perfect, but we try.)