Actually, "Pray the Gay Away" was not the Exodus slogan. I don't think Exodus made the claim that prayer could turn a man heterosexual and abolish same-sex temptation once and for all, forever. They just made the reasonable and true statement that prayer can help a man reduce
obsessive gay drives and live in a chaste and honorable manner without sodomistic conduct.
"Pray the gay away" was a mocking caricature of that, invented by their LGBT opponents.