"I once hounded one of my friends who is Catholic, trying to get her to come back to my (Baptist) church, where she had been before" ... "I just didn't want her to go to Hell, because I like her."
So, according to this guy, Muslims, atheists, and even Catholics(!) are going to Hell? Wow, if this loon is right, it's going to be awfully crowded down there!
Back to the issue... There are some religious people who think that atheism is a bad thing, and that atheists are somehow more likely to lead immoral lives. Of course this is total nonsense, but many of these people have not met many atheists, so they are full of misconceptions about those who do not believe in God. Heck, even George Bush Sr. has stated (back in 1988) that atheists cannot be considered good citizens and patriots. Fortunately, most people of faith, even deeply religious ones, are much more open-minded than that, and realize that religion, including one's belief in God, is a profoundly personal matter.
You may want to go with your friend, for curiosity's sake, but if that doesn't make him stop, explain to him politely but firmly that religion (or lack thereof) is a personal matter and that his efforts to convert you make you uncomfortable. if he's a good friend, he will understand and respect your position.