Honestly, there is one thing (in my opinion) that separate true Christians from false ones.
True Christians (in my opinion) live by the Bible and by the God of the Bible (meaning that they let go of things that don't line up with the Bible (I'm saying Bible a lot, aren't I?).
Those people who cruelly condemn others? Well, they're not true Christians, because they're living in hate, and God calls us to love everyone. As long as someone lets go of any sin they were holding on to, no matter how late it may seem for them, they can be a Christian - it's not an all exclusive kind of thing. It was never meant to seem like an all exclusive kind of thing either, and false Christians are leading others away by making it appear that way. We don't have to be perfect, and the hypocrites that act so aren't. Lastly, (sorry that this is kind of disorganized) true Christians seem to have this loving quality that's easy to see but hard to explain - like this light that's inside of them but kind of shines on the outside, too. There are a lot of other things in the Bible that (through stories, parables, and the like) separate true Christians from false ones, but I'll end this here.