they are not religious or is it not know to them these two verses from the scripture. thats the most simple answer if you believe that Torah is from heaven.
Vayikra 18:22:
You shall not lie down with a male, as with a woman: this is an abomination.
Vayikra 18:29:
For anyone who commits any of these abominations, the persons doing so shall be cut off from the midst of their people.