I am no authority on homosexuality. All I really know is that I meet a lot of gay folks here in Berkeley, and they are every bit as nice as anyone else.
Nor am I a genetics expert. But I know enough to hold a discussion.
You are right that there may be no genetic connection with homosexuality, because it doesn't seem to be inherited in general. But there are intriguing differences such as digit ratio, and we know that many developmental differences can have a genetic factor. Who knows what we will find?
I think the flaw with your argument is that you are assuming that homosexuals don't breed. Not true, and there may also be factors increasing the success of their offspring such as small, educated and relatively affluent families.
Next, do not assume that direct reproductive success is the only possible pro-survival factor. The contribution of homosexuals to the reproductive success of their close genetic relatives or even their community may be a pro-survival factor for genes like their own.