I sort of see the OP's point (at least, what I hope was his point).
While events that promote understanding and tolerance are great, there may be a slight risk that some of them serve to reinforce perceptions of difference. Perhaps perpetuating an us-and-them artificial separateness.
If the point is to celebrate those differences, and specifically to highlight the contribution made by that group, then fair enough. Unfortunately we are surrounded by knobheads who do not celebrate variety, and who are hostile to anything that doesn't conform to their template, which is where the risk comes into it.
If the point is to advance the acceptance of all colours, flavours, orientations etc etc, then perhaps that aim might be served by promoting events that include everyone. Thus at a gay/lesbian event, have performers who are gay, bi, straight and all stations between. The point of the exercise, namely the promotion of acceptance of a spectrum of sexual preferences, would be served, but with the active inclusion of everyone. It would be more a living, breathing example of acceptance and unity than an event where only one group was allowed to perform.
I think I've probably explained my thinking pretty badly...
Events where all performers are a member of the group whose interests are to be promoted are fine, and I support them. Just saying, maybe they miss an opportunity.