Will pessimism eventually lead some people to suicide? You don't have to literally devalue everything and anything in life to be a pessimist. Tangentially (i like that word), becoming disenchanted with (the joys of?) life and/or living in near-constant acknowledgement that terrible things can, do, and will happen doesn't make one a pessimist.
Also worth mentioning, just being rude is a separate thing altogether.
Pessimism seems to be an internal way of thinking aka a philosophy that a mentally sound person who does not have a mental complex can choose (or is otherwise forced to) embrace. I imagine the two get confused often.
And anyway, being too happy can lead to suicide too lol. Albeit at much lower rates but- yeah. The afterlife ie. "why am I wasting time in this dump?", etc.I gather you define suicide as a sudden and willful action to stop one's heart but there's plenty of other ways. A life of drugs and drinking, etc.