How can you tell the difference between a real Christian and a fake Christian? I work with a man who claims to be a Christian, but if that's what a Christian is, then I don't want to be one. He treats other people like dirt, and I wouldn't trust him to keep his word no matter what he says. — H.P.
Only God knows our hearts, and only He knows whether or not this person has sincerely put his faith in Christ as his Lord and Savior. Jesus warned, "Do not judge, or you too will be judged" (Matthew 7:1).
From what you say, however, this person is at best an inconsistent Christian—and at worst, not a Christian at all. Jesus commands those of us who are His disciples to love people, not to treat them as if they were below us or are worthless. He said, "By this all men will know that you are my disciples, if you love one another" (John 13:35). The Bible also says, "Let your gentleness be evident to all" (Philippians 4:5). Needless to say, a sincere Christian's life should also be marked by honesty and integrity.
Don't let the hypocrisy of one person keep you from Christ. People may disappoint you—but Christ never will. Look at Him as He is revealed in the pages of the New Testament—and when you do, you will realize that He was the perfect example of love and self-sacrifice. The reason is because He was more than just another religious leader. He was God in human flesh, sent from heaven to save us from our sins by His death on the cross.
In other words, take this person's life as a challenge—a challenge for you to discover what a true Christian really is. Then by faith give your life to Jesus, and let Him begin to transform you from within by His Spirit. No, Christians aren't perfect—and we won't be until we get to heaven. But until then, He is with us and helps us every step of the way.