Other than these?
1. We don't actually have the knowledge of any planet that would work nor the technology to transport people there; and
2. Exiling people who do things we don't like is patently offensive
Well, I don't imagine it would be a mean-spirited "exile". Think more "Free Willy" and a "Go, make us proud" attitude. And when they finally do leave, we'll watch them depart in giant spacecraft and think "well, there they go..." "Let's hope the best for them".
How on earth would it NOT be mean-spirited?
*Ahem*... Imagine an overcrowded, obsolete Earth. Now imagine a lush, virgin, tropical beautiful Homoearth. Through the use of strategic, positive propagnda, and systematically showing through media how beautiful Homoearth is, we would peacefully convince all gays to move the the new Eden-like world while straights wish them the best as they depart in giant spacecraft.