It is not for us mere mortals with our myopic vision to presume to understand the full extent of the Divine Purpose. As Gandalf said to Frodo Baggins, "even the very wise cannot see all ends." But Mother Nature can give us a clue about why gay people exist: built-in population control. We're very effective in that way, and in this age of severe overpopulation and quickly-depleting natural resources (Go see "Inferno" later this month) we gay people represent an under-appreciated natural resource that ought to be applauded for not breeding rather than reviled.

And for the record, I resent having my gay ontology referred to as "a departure from the Divine Purpose as a result of the Fall," unlike your presumably straight ontology, which in your way of thinking is consonant with God's will. That is deeply offensive and not very Christian of you.