Re: "my suspension of disbelief finally broke"
I think you'll find that many gay people procreate. Sometimes they grit their teeth and do it the old-fashioned way, because they want children, sometimes they use medical intervention.
I wouldn't call a minority preference 'deviant', especially when it is so deeply embedded. That would be to suggest that all left-handed people are 'deviant'. Right-handedness is the majority 'practice', but that means nothing at all. It just is.
Showing minority 'practices' is not teaching sex-ed, it is showing the world as it is. Children who are cocooned to believe that the world is just mummies and daddies are not being helped to face the world they'll live in when they grow up.
However, I always suspect a lesbian kiss or sex scene, as it always seems there to titillate the male part of the audience than for any plot-driven reason (I am speaking more widely that Dr. W) From a rough count through memory-land, I think it's about eight women-women kisses to men-men kisses on TV. Strange bias...