As a scientist he understands that if homsexuality were truly an hereditary trait, it would have disappeared from the gene pool long ago because homos can’t reproduce and pass the trait along to their offspring.
Thus by scientific definition, human characteristis that are not hereditary are learned. In other words, the result of a conscious choice.
There you go again...using reason and logic in an emotional argument, that is not allowed and the libs will call you a homophobe, racist, sexist and other nasty names.