Romans 2:17-24
17- Now then if you call yourself a Jew; if you rely on the law and brag about your relationship with God;
18- if you know His will and approve of what is superior because you are instructed by the law;
19- if you are convinced that you are a guide for the blind, a light for those who are in the dark,
20- an instructor of the foolish, a teacher of infants, because you have in the law the embodiment of knowledge and truth -
21- You then who teach others, do you not teach yourself? You who preach against stealing, do you steal?
22- You who say that people should not commit adultery, do you commit adultery? You who abhor idols, do you rob temples?
23- You who brag about the law, do you dishonor God by breaking the law?
24- As it is written: "God is blasphemed among the Gentiles because of you."
OK 2 points i would like to make here: The Jews were the people back in the day who were known for living lives for God, The Gentiles were people who didn't know God or much about Him.
Let's modernize: Today Christians are known for living lives for God, and people that we call "Lost" don't know God and often, but not always, know very little about God.
So here is the TMPV (Tony's Modernized Paraphrase Version) of this same passage of scripture..
So, you call yourself a Christian, you go to church and "know" you have a "good" relationship with God.
You know how He wants you to live because you go to church almost every week, some weeks several times, Hey! you might even be a "Sunday Nighter"
You have something to offer your lost friends, you have a testimony to share with them, because you have actually studied your Bible a little.
So you want to help other people out, are you helping yourself?
You complain that people are unloving, are you unloving?
You gripe when people judge others, who are you judging?
You get mad at people who act all "religious", do you ever act religious?
It upsets you when your friends sin, in what ways are you sinning?
When you feel good about yourself because you are doing the church thing, do you turn your back on God by the way you act outside of church?
God is disliked, hated, and talked bad about all the time by people who don't know Him because of the way we, as Christians, act.
I know that before i became a Christian i was turned off the Christianity by some Christians i had encountered.
Bottom line question: Are your actions and attitudes as a Christian making God look good...
or bad?

To many people we are simply polluting the world of faith with our attitudes of judgement, unforgiveness, and exclusiveness.