Personally, I think it's arrogance. I have dealt with this my entire life as well and I'm a Christian.
Here's an example. I know a Christian family that once upon a time were very loving, accepting, generous, and sweet. They were frugal, and cared about others. They helped those in need. Then, something happened. I'm not sure what. They changed. Now they drive expensive cars, live in houses that they can't afford, and are completely isolated from anyone in society that they feel is beneath them. All the while, proclaiming they are Christians. They have openly scorned others such as a Jewish girl and Catholic man who were going to be married to Christians.
These same people also have excluded Christians that they feel are not worthy or underneath their beliefs. They have chastised many for being undisciplined in the Word of God and for not having perfect lives.
When I got a divorce, these people were the first to tell me that my reputation was tarnished and I needed to learn to live above reproach. Even thought they knew nothing about my personal life or the fact that my ex was abusive.