Speaking as someone who has spent multiple decades in niche Internet communities, I can vouch that in many cases, it's taken out of context when talked about or observed by a third party. Sometimes (often?) it's not as much of an attack against another person as it appears, and sometimes it's just outright satirical. It's your prerogative to judge how you see fit, but by doing so you legitimize an orwellian crackdown on free expression (and please spare me the tired argument that that's okay as long as it's not state-sponsored).
From my point of view, a person's conduct on the Internet when pseudonymous does not necessarily reflect on a person's ability to conduct themselves professionally at the workplace or in front of customers.
Is there an epidemic of people spouting off at the workplace? I must have missed the memo.