This problem predates the Internet and is a strong argument against mob violence as a form of protest. For example race riots in the US invariably occur in low income black neighborhoods, and the result is a bunch of black businesses get looted and destroyed. The mob is not capable of going to where the elite are and doing real damage to them so instead they trash their own neighbors and perpetuate the cycle of oppression. Similarly the cancelers tend to participate in communities that largely share their views and then destroy those communities over minor affronts.
The context in which the GP was speaking was running a forum. I've responded to it.
You've responded by going on tangents about personal blowback for personal activities and, strangely enough, protests.
That's not the threat vector that people trying to self-host forums tend to face - and even when it is, it's not that different from regular, run-of-the-mill mill stalking/and/or/harassment/chan-board-brigading/sub-brigading that anyone running any forum, self-hosted or not has to deal with.
[1]: Largely accidentally, as they earn it through being the most "pearl-clutching"-iest community on the internet.
You might also discover that bakeries might not want to bake swastika cakes for you, venues might not want to be let out for hosting your marches, decent advertisers might not want to run ads on your podcast, etc, etc. It's a free country, just because someone's being a monster doesn't compel me to do business with them.