Even so, I would expect nature to strongly select against it. If the case is that it is a recessive allele then selection should play a part on it as it does for every other recessive allele. If we're dealing with genes that code for bisexuality rather than homosexuality altogether, I would speculate that it is still a deleterious gene. Only half of those genes should be passed relative to genes for heterosexuality. If the gene had not been eliminated, you should expect to see some sort of decline. The fact that we fail to see any is an enigma to me.