Do you have any data on homosexuality being passed from generation to generation?
You're making a common mistake in assuming that if something is genetic it must be passed on through the generations. While most often that IS the case, not always. A few examples: after fertilization, a gene in the embryo mutates. Neither of the parents had this particular genetic construction, but their offspring indeed does. It is certainly "genetic," but not "hereditary."
Here's another: each of us (other than identical twins) are unique combinations of genes coming from each parent. The unique mixture produces an individual who, based on that precise mixture and interaction among the genes, is constructed in ways unlike their parents. For example, Isaac Newton's parents certainly weren't as smart as he was, but their genes (and whatever particular environmental factors) combined to produce--arguably--the greatest genius of all time. And, I'll bet that Denise Richards' mother is no way near as good looking as she is. So, the way the new combo of genes works together is unique to that individual and can never be passed on precisely in the same way--other than with a clone. Genetic--but not directly hereditary.
Male homosexuality is probably a particular combination of genes that is likely a fellow traveler with other traits--some of which we associate with gay males. Can environment affect sexual behavior? Of course--but IMO only in the extremes. For example, if a man is imprisoned for ten years and has no contact with a woman (and has always been stimulated by T&A) but now after isolation has a sexual encounter with another male, is he gay? No--I don't think so; he certainly engaged in a homosexual act, but his orientation is still straight since he will be exclusively with women when he gets out.
Since homosexuals--by their behavior--take themselves out of the gene pool, it is an interesting question and one that more answers await more research.