... then why are there atheists? RC Sproul wrote a book by that title and, though I haven't read that book, I studied and preached on Romans 1:18-21 last Sunday which talks about unbelievers "suppressing" the truth in unrighteousness and says that there is absolutely no excuse for unbelief.
Paul's point is that the reasons for unbelief are not intellectual but moral and spiritual. People love their autonomy and pride and do not want admit their need of Jesus' death and resurrection, nor submit to God's rulership over their lives.
Ask your unbelieving friend: "If I could show you that the evidence supports Jesus' claims, would you bow down before Him, accept His salvation and submit your life fully to Him?"
It is because they do not want to do that that they manufacture reasons for not believing in God. People believe what they want to believe. When confronted by reality they do not want to accept they go into denial.
I've witnessed to people who raise objections faster than I can respond; often they don't even wait for my response before going on to the next objection. They don't want to know if their objections are sound, they just want to show me that they can generate objections faster than I can answer them so that I'll stop talking to them about Jesus.