It may be a behavior learned by feedback, but that doesn't mean that there aren't strong social norms against it. When I mentioned to a friend my intention to write this article, the first thing it made her think of was a comedian who said that, as a strong Christian, one of the most discomforting things he could hear someone say was "I'd like to talk to you about Jesus." Similarly, consider all the people who take dietary restrictions on themselves for moral rather than health reasons, but are uncomfortable seeing people try to convince others of that same position. These people have internalized a value that causes them to react negatively to others confronting people on closely personal beliefs.