Listen the at least the first part of this show, Archive - This American Life
It centers on the effects of someone being a pessimist.
It is unethical (and illegal) to have something like political, sexual, age, race, creed have bias in discrimination. Of course it is going to happen everyday, so just don’t talk about it, bring it up, or ask/answer questions about personal stuff. Most things probably won’t hurt you too bad, say if you were a Mormon , no big deal as long as you keep personal agendas to yourself at work. If you were a Grand Wizard of the KKK, well then people might not like you to be around as much, but if you keep all that at home, and you are fine at work then there is no reason to fire you for it.
It is also unethical to openly air things like political, sexual, age, race, creed at the work place.