Yelling out "Fuck!" because you just stubbed your toe on your desk, or because you've been stuck on a frustrating problem for awhile that you just can't solve, is fine. Saying "Why does team X's product suck so fucking much?" or "Why do you keep making this same fucking mistake?" is a huge problem.

It's not exactly about the swears per se, but about being overly negative / anti-collaborative. The OP post gives off the vibe of someone who prides themselves on being "brutally honest" in their feedback but which in fact really just comes off as being an asshole to most people.