It is not a sin. I don't care what the bible or whatever has to say about it. Homosexuality is merely an anomaly. Whether caused by genetics, in utero problems, or problems with the family after birth, it has obviously not "harmed" the ability of the human race to vastly overpopulate itself.
BTW, homosexuality is common in many other species also.
There aren't any real problems with it. Let them b-f each other or c-l each other. It's no one's business but theirs.
Now the benefits include providing a good source of jokes, interior decorating, and "La Cage aux Folles".
BTW: On reflection, there are a couple of problems:
1) An old friend of mine, Gaylord, resents the takeover of the word "gay". He can no longer introduce himself as "Hi, I'm Gay."
2) The great old 1930s and 1940s songs with the word "gay" in the lyrics now elicit snickers.