Any relationship, aside from marriage, is a limited one. Your relationship with your boss is based on exchanging trustworthy and valuable labor for money; that's the primary standard by which he should be impressed with you. Of course, it's not all about results: character plays a role, too, but only what the job requires.
Cultivate good virtues, and let others think of you what they will; keep close to you those that are impressed by you, and let the others go on their way.
You mentioned not being able to know that they're rational people. That's okay - they only have to be rational enough within the context of the relationship; anything else is theirs to deal with "off the clock". Leave out things that don't matter. Who cares if your boss is a Christian, or a bass fishing enthusiast, or Celine Dion fan, or anything else (rational or not) that doesn't matter at work? What matters is: does he treat you well, pay you fairly, and acknowledge your work? Or is he a micromanaging buffoon who sabotages your efforts?
Leave out what doesn't matter, and you'll not only be able to focus on the values that will get you ahead in life, but you won't be distracted by your judgments of the unimportant aspects of the lives of those "higher up the chain".