It's the clash of left-wing absolutes:
on the one hand the scientist may prove that being gay is encoded in DNA,
and
on the other hand people may demand to abort gay offspring(detectable via a DNA test).
What does the Left do?! They must have abortions, but they can't let people abort gay babies...
...thus, the Left seethes with rage at the mere possibility that the issue is even being studied.
It appears that they even object to gene therapy. I am sure that they will fund a research which can turn a normal people into gays.:-)