A: I certainly agree with one thing you say: Christians are supposed to be kind and good. Jesus said, "By their fruit you will recognize them" (Matthew 7:16).
When they aren't kind and good, it's because they've fallen short of what Jesus wants them to be. Jesus commanded us to follow Him and obey Him -- and when we do, we'll become like Him in our love for others and our moral integrity. A person who claims to be a Christian but is selfish and thoughtless may not be a Christian at all. The Bible says that when we truly follow Christ, we will be "pure; then peace-loving, considerate, submissive, full of mercy and good fruit, impartial and sincere" (James 3:17).
Can people who don't believe in Jesus (or may even be atheists like your friend) also be kind and good? Yes, of course they can. Although they don't realize it or believe it, God created them, and He implanted within them something of His goodness and love. At the same time, they'd be even better people if they opened their lives to Christ's transforming power.
Don't let the bad example of a few who claim to be Christians but aren't really following Jesus keep you away from Him. God loves you, and He alone can take away your sins and give you hope for the future. Commit your life to Jesus Christ, and discover the joy of following Him every day.