Why don't scientists try harder to prove homosexuality is not a choice?

By proving it, they can end so much discrimination against so many innocent people. How come they can find explanations for all kinds of mental illnesses and psychological and medical conditions but not this one? The close-minded will never agree that homosexuality is not a choice. The only solution is to find the gay gene, because unless the evidence is concret, there will always be a lot of nutjobs who will argue the conclusions based on psychology may be incorrect the same way Freud's ideas are not proof of anything. Find the gay gene and the problem is solved.