They joined the Church to judge and condemn those who aren't as holy as they perceive themselves to be. Interesting the similarities between Christianity and Islam in this - few other faiths seem to have much of a problem with attracting these types.
True Christians aren't self-righteous. They are humbled by the depth and breadth of God's grace and mercy, which is only available through the cross of Christ.
Going to a Christian church doesn't make you a Christian any more than going to McDonald's makes you a Quarter Pounder. As Jesus Himself said, you must be born again.