The fact that you're a Christian doesn't mean that you are without sin. It means that you are forgiven. However the Bible does say that we will be forgiven the same way we forgive others and with our own measure it will be measured unto us. Luke 6:37
The way some people go around pointing out the faults and short comings of their neighbors is what keeps a lot of people out of church. Being a Christian doesn't mean you have a right to tell others they need to pull up their socks and act superior to them. Jesus was The Son of God and He was humble, patient and forgiving.