That disgust is part of instinct. Its also the same drive that makes some of us straight folk sometimes queasy at the thought of gay sex. Your body's ultimate goal when calibrated specifically for genetic success is to find a mate and reproduce and care for family from your own species. We're all wired different though. Its easy to judge when you're normal. If I found out somebody was switched on by something weird, I'd reserve judgement based on their actions though because despite our drives we are NOT animals. Human beings are creatures capable (though not always willing) of superior reason and self restraint.