Have you ever heard the expression "hate the sin and love the sinner"? I have but it sounds more like a cliché than a useful theological statement. It's actually very telling of how God's judgment works.
So often people refuse to believe in hell (or insist that it is empty) because God is perfectly merciful and loving. They assume that mercy and love means to overlook sin; as opposed to forgiving it. There is a big difference between these.
Overlooking someone's faults means that they remain unchanged. Instead of calling sin "sin" it would be called something else. We think God will say "oh, you're not that bad... come on in!" Forgiveness, on the other hand, requires that we repent. Repentance means we turn away from our sin; we cut it out of our lives. We remove it from ourselves.
Do you see the difference? In the first case (God overlooking sin) we would bring our sin into heaven with us. How could this be possible? How can sin exist in heaven? We would necessarily need police; rules, and laws. We would hurt each other and ourselves. The presence of sin is the cause of every problem on earth; how could heaven be any better than earth if sin also exists there?
God forgives sin because that means we will enter sin without it. "Nothing unclean shall enter it" (Rev 21:27) and isn't it simply logical that it would be so? Isn't it obvious that if we want to enter heaven we have to leave sin at the door just like a person entering a mansion would need to leave their muddy shoes outside? In this way God hates the sin (will not allow it into heaven) but loves the sinner (will allow him into heaven). Isn't that neat?
But what of those who won't take off their muddy shoes (sin)? What about people who love their sin too much to repent of it and set it down? Now we have a difficult situation because the sinner has identified himself with his sin. He has made his sin a part of himself. God cannot allow sin to enter heaven, as we have seen, so what is the obvious result of a sinner who refuses to let go of their sin? They may not enter either.
How many times has God been blamed for "condemning" people when it's so clear that only we can condemn ourselves. In his perfect love and mercy he is always ready for forgive those sins we are willing to cast aside but he will not force himself upon us.
In the end, it's not God's choice between accepting or rejecting us. It's our choice between keeping God or our sin; we simply cannot have both.