You should certainly be nice to the janitor: They are not part of office politics and so can afford to just interact naturally and decently.
Conversely, people are careful to stay on guard to threats and opportunities in interpersonal power-games, and so when they see the janitor, the fact that politics does not apply makes them relax and behave naturally: This is either rudely or nicely, depending on the individual's character.
Conversely, people are careful to stay on guard to threats and opportunities in interpersonal power-games, and so when they see the janitor, the fact that politics does not apply makes them relax and behave naturally: This is either rudely or nicely, depending on the individual's character.