That in itself is overstepping what Christianity is about. At the core, you only need to believe a few things:

1. Jesus is God

2. God is Triune

3. Baptism unites us as Christians

Everything else varies from one denomination to another. Also, if you’re going to put any restriction on c/christians are you also going to going to apply this equally to other communities of similar faiths like c/jews c/muslims? The belief systems are very connected to the Old Testament teachings, where most of the discussion on this topic stems from in theological terms.

https://en.wikipedia.org/wiki/List_of_Christian_denominations_affirming_LGBT_people

At the heart of Christian teaching is love. Following a personal conviction of self-applied beliefs because you think God’s vocations are more important than your brain chemistry is just that: Personal. It should never spill over to anyone unwilling to follow such a path, especially in a way that is hateful. I think as long as participants understand that line in the sand is a line in stone and it is carefully moderated, then it should be fine. There’s literally millions of other topics that could be discussed.