How do I explain to my son that being gay is wrong in a non-offensive way?

If this is true then yea I think he is mentally sick. Molestation from same can and does cause desires when you are older. He has this beautiful family and is deserting them for this sick . If you are really gay then thats fine but he is NOT he is just sick and sadly was robbed of some of his innocents. I imagine he feels disgusting and very depressed right now. Something like that can become an addiction however.