Gene for homosexuality

This a controversial issue.  I am not going to say that homosexuality is
or is not casued by genetic influences.  However, the fact that homosexuals
do not have children, however, can not be used against the genetic argument.
For example, Tay-Sachs is a genetic disease in which the affected patients 
die before they reach sexual maturity, therefore preventing these patients
from propagating their faulty Tay-Sachs gene. By your logic, one might think
that as these people died, the frequency of the gene would decrease.  This
 is not the case.  There are at least two reasons for this.  First of all,
the reservoir for faulty genes is in the unaffected heterozygotes, whose 
reproductive success is not decreased, i.e they have no disease and can
 pass on their faulty gene to the next generation.  Secondly, mutations can
arise de novo.  That is you get the disease not becasue you inherited a bad
gene from your mother and/or your father who had the disease, but the gene
somehow became mutated in your parents gametes or early in your development.
I do not mean to make any judgement of homosexuality by comparing it to 
genetic disease, this comparison is made usely as a teaching tool. Again, 
whether or not homosexuality is or is not due to genetic factors is unknown, 
but your selection argument is insufficient to argue against it.