I just had a similar conversation with an old school mate I run into every once in a while.

Anyways, I have a psychological theory about this attitude. I kind of doubt I invented it; more likely I haven't run across it in amateur research.

When many people have made a dissonant value choice, they tend not to confront that choice. Rather, they solve their internal dissonance by trying to convert others to their side. When they get their conversions, their dissonance is relieved.