I’m sorry, “gay vespers” is horrible. Vespers is part of the liturgy where we should be focused on God, not attachment to sexual sin.
We don’t have “adultery vespers,” fornicator vespers," etc. And if you say “oh, it’s about culture” – we don’t have “African American vespers,” “Italian American vespers” etc.
We simply have vespers in a language and all pray it together, as a parish community. Singling out one group (regardless of who it is) is 100% wrong.
If I was the OP, I would send an anonymous letter to the priest (if you are still afraid of the priest) and then a signed letter to the Bishop if nothing changes.