There are two fundamental mistakes displayed on this billboard.
The first is that being gay is not something you are born with; thus, it isn't "real."
The second is that homosexuality is a "behavior," which makes to idiotic assumptions: that all homosexuals behave the same way, and that even if a given homosexual were to be completely abstinent, somehow that person is "sinning" by simply being homosexual (so no chance of redemption - you're damned for what you are, not what you do; no sense in bothering to "good" - you're damned anyway).
Which is all a sort of loop: you can't be gay because homosexuality is not real and thus a choice, but because you really are homosexual after all, you're condemned.
I wonder if any of these fear-filled, pro-hatred types have ever had a complete think about the contradictions they spout?
So let's call it what it is: condemning/excluding someone for who they are is apartheid, and the first step toward genocide. It's ugly - but there it is. And I think we should start to call it what it is.