I've asked the same thing about atheists before, but more from the angle that if God knows everything about everyone, and knows what actions and decisions we make long before they're even thoughts in our mind, then why would He bother to create anybody whom He knows will reject/renounce/simply not believe in Him and/or not accept Jesus? In a way, it seems to me to be equivilent to, say, an artist spending a great deal of time crafting a beautiful painting that he knows he's just going to destroy and throw away anyway. Why bother?
The way it's been explained to me is that we all have free will to make our own decisions, and that if we weren't, then God would not be a god, but rather, a dictator.
Still, there are some preachers out there who kind of make the concept of free will a gray area: they say that those who become Christians are pre-destined to do so by God . . . I get what they're trying to say, but to put it like that, really does make it sound like God's unconditional love for all people is, indeed, conditional, and that He picks and chooses who He loves, rather than loving all, like Christianity teaches.
It does, actually. The Bible says that for a man to lay with another man as he would with a woman is an abomination, and although Jesus died for our sins, that doesn't entirely give us a free pass to wilfully engage in sinful acts (which they would consider homosexuality to be). Of course, we all have to answer for our actions when we reach death, so for all intents and purposes, whatever LGBT people do - even if they are Christians themselves - the only ones they have to answer to for that is God . . . but, some preachers will put it bluntly: if gay people don't stop being gay - even if they've accepted Jesus Christ as their Lord and Savior - they'll still go to **** for not being repentant of their gayness.