I dispute the statement that," homosexuals cluster together because of stigma and discrimination".

There are three openly homosexual couples in my area (approx. thirty square miles), that I know and work for periodically, all three couples have lived here for over ten years, and have never faced stigma or discrimination of any kind....according to them.
All three couples are over sixty.

There is one single homosexual, who spends every weekend in a major city...."because of the night life". Apparently a sexual free for all exists in the larger city areas, this could well be the cause of the "cluster syndrome".

This hedonism amongst MSM, is thought to be a big factor in HIV transmission and is mentioned by the agencies when referring to the "open marriage", Union, relationships, linked to earlier.