As far as I know if someone doesn't believe in a divine entity that is the source of morality he/she considers morality to be subjective. He/she believes morality exists to minimize the pain and maximize the pleasure of humankind. Something is decided moral or immoral according to that by collective subjectivity.
So my question is that aren't we applying double standards in terms of classifying gay, lesbian, trans sex as moral but classifying incest, pedophile, animal sex, underage sex etc as immoral? I think everything should be legal until proven harmful or they should be illegal until proven safe. Because that will minimize the pain of the individuals. Even though something is harmful to individuals itself can they still willingly accept to act upon it without legal intervention? Because that will maximize the pleasure of the individual.
You can apply this principle to any kind of act. I'm bringing up sexuality because it is becoming the social norm. But I don't believe we do understand what morality actually is. Can you enlighten me please?