It doesn't happen often, but occasionally I will run into someone who will have an arsenal of tough questions. I know that this can be scary and in fact many will tell me that their worst fear is not being able to answer someone's questions. However, I have learned that God will never give us more than we can handle. Another thing that I have realized is that answers do not turn a sinner from his ways.
Man: Do you know what I don't get? Why is it that prisoners that have committed horrible crimes like murder can still go to heaven?
Me: Well, I think you may have a problem with thinking that you are better off than the murderer.
Man: What do you mean?
Me: Jesus said that if you have hated another man you have murdered him in your heart. Have you ever hated someone? He also stated that lusting after another is committing adultery. Have you ever had a lustful thought?
Me: Lied or blasphemed his name?
Me: By your own admission you are a lying, murderous, adulterous, blasphemer at heart. What do you think God should do to you?
Man: I see your point. I never looked at it quite like that before. Do you think homosexuals are going to hell?
Me: Have they ever lied?
Man: Who wrote the Bible?
Me: The Bible says that all of Scripture is "God-breathed" and that holy men of God spoke as they were moved by the Holy Spirit. God wrote the Bible using man.
Man: How do I know that it is true?
Me: Read it. Examine the claims.
Questions can be rabbit trails, but I felt like he was sincere. Don't be afraid to say I don't know if you do not know the answer, and always go back to the gospel. Personally, I love the tough questions. I wouldn't know half the verses that I have memorized if I wasn't stretched every now and then.