Key word there was rationalization. If terminology is the problem, replace "egoism" by "selfishness" and my point remains the same.

I don't buy rational egoism. What is rational is whatever advances one's goals - goals which may or may not be selfish. Considering our inbuilt empathy & love for our families, the general case is that our goals will not be purely selfish.

Even if I was a rational egoist, though, actually believing something against evidence (as distinct from declaring belief or not caring) is utterly irrational.