If you express your opinion on a private forum instead of a public one, you're much less likely to be crucified for it. I can make nasty off-handed comments to my friends in private chat all day, with very little fear that it'll see the light.
Ultimately sheer quantity of people is the bigger problem than anything else.
It's possible, but it's far, far less likely than a post on social media with your name tied to it - it's also completely deniable and contains only usernames.
This crosses the Internet boundary too - see e.g. the well-known case of a guy who lost his job because someone overheard his meatspace conversation and decided to post it on-line...
Ultimately sheer quantity of people is the bigger problem than anything else.