I'm also not sure that it's a matter of having these people move in. But that may have been a bit of literary flourish.
I do think that the "normal" people largely got out of the gay rights movement. They weren't people who built their lives around some kind of sexual persona, or identity, they had work and friends and such and didn't need to socialize only with certain people based on their sexuality.
What this has meant is that to a large extent the people who get so involved in these kinds of organizations are people who see sexual identity as key to who they are, or want it recognized, want some kind of separate gay culture.
If I'm honest, 90% of the people I meet who are heavily involved in these kinds of organizations, many of whom I deal with at work, groups presenting themselves as representing the whole "community," seem to have other kids of issues. Autism, anxiety, whatever, they are the people that are looking to label themselves with every trendy diagnosis.
The gay and lesbian people I know who are "normal" (loaded word I know) and down to earth - and these are a lot of people from many walks of life - aren't interested in these groups and don't see themselves as having anything in common with the people in them. This isn't a new thing, they've been like this for 20 years or more. They aren't into flags, or Pride, and their politics are all over the place.
What this all means though is the groups are being shaped by a group of people who are in no way typical, and often seem to have issues.