I have a friend of mine from my childhood who is a completely different man. He tells me nowadays that he believes that God and Jesus Christ are extremely evil people who are just out to destroy everyone eventually. He doesn't believe that Jesus is good and literally hates him. He truly believes that Jesus has a very, very, dark heart. I am confused because I don't know where to start. Any advice?
I take it that you have had at least one conversation with him about this. How did it start? Is there opportunity to bring it up, or does he provide the opportunity by starting it? First you have to feel free with him to talk about it, and if so, you have to stay on point and not let him lead you down a dark path. You can't be lost where you have nothing more to say. At the very least, you need to be able to say that you're sorry he has such a dark view of God, and that you don't believe the way he does.
It seems to me that you need to know the gospel like the back of your hand. What you're trying to do is called apologetics, or "defending the faith" (Jude 3). Unbelievers have objections, and we should be able to answer them with knowledge of the Bible, in order to reach them (or others thinking the same thing who are not activists) - 1 Pet. 3:15. It is likely that he doesn't see the hope that is in Jesus, so he fears death and eternal condemnation, and thus has created a justification in his mind to reject the message of truth. It is very difficult for a person to live with a guilty conscience.
Ultimately, you need to ask yourself if his friendship is worth keeping. Paul wrote "be not unequally yoked together with unbelievers..." and this could apply in just about every area of life. There was a point at which I had to forsake all my unbelieving friends, because their influence on me was not good for me. Some of them no doubt said "good riddance." Nevertheless, Jesus' emphasis was on doing good, saying "let your light shine before men so that they see your
good deeds and glorify your Father in heaven."