What is a more modern interpretation of the terms egosyntonic/egodystonic?
Cognitive dissonance theory seems to be exactly what you're looking for. It seeks to explain how and why people hold incongruous or dissonant beliefs. I guess egosyntonic beliefs would be consonant with self, egodystonic would be dissonant. Anyway, I'll just link you to the Wikipedia page:

http://en.wikipedia.org/wiki/Cognitive_dissonance