Who laid this foundation?

One of my co-workers was telling me about a "Christian" friend of his. He told me that this friend was protestant, or something like that. He thought this friend was a little messed in the head because he would swear, drink, fight, do drugs and would even curse at his own mother. However, if anyone tried to use the name of Jesus Christ in vain he would freak out at them, so they knew never to do that around him. Hearing this story made me think that this "Christian" was probably using the name of Christ in vain in a much worse way than any of his friends. I am a hopeless sinner myself, but it saddens and angers me to hear of this fellow, and to think that he may be the only example that his friends have ever had of a Christian. I think that there is a necessity to question the activities that we participate in, and to weigh them in light of the word of God, not the way of the world.