Careless Lives Cost Talk

In a book that I recently finished, Mere Christianity, C.S. Lewis makes arguments for living a "christian" lifestyle.  At one point in the book, he urges Christians to live responsibly and "like a christian" because, "careless lives cost talk."  This, of course, is a play on the war poster to the left.

I think that this is a really insightful way into the way that humans, myself included, judge groups of people.  He said that when people see Christians acting poorly, it gives all Christians a bad name.  That is definitely true, I would be lying If I hadn't ever seen a Pat Robertson quote and gotten mad at all Christians as one.

Is it fair to group people like this.  On the one hand, Christianity is different than say race or gender.  People do not choose these traits, but they do choose religion.  If you have all chosen to be in this religion, you must all be like-minded, right?

That doesn't make sense, how can the millions or billions of Christians who subscribe to the words written in the Bible be assumed to have the same interpretations of the book, or even the same actions.

This seems to be something that I will have to work on: not judging whole groups en masse.  Have you ever judged a whole group based on one person only to discover that you made a gross miscalculation?