All forums/boards are autocratic by design, so there's no such thing as an unjustified ban in the first place. The difference is how the userbase reacts to these bans, and their options are staying or leaving.
The userbase tends to stay when they overall feel that these bans were taken as a last measure. The userbase tends to leave when they feel that bans are used willy-nilly or for nefarious/selfish reasons (just because a ban can't be unjustifiable doesn't mean a ban can't be bad, since actions will usually lead to reactions).
The vast majority here seems to be in favor of staying because they trust, by experience or by proxy, that Toady does a good job overall about banning people, using it as a last resort when all other options have been exhausted.
Plus, as some people have pointed out, people can, in theory, always return with an alt, it doesn't require mental gymnastics to mask oneself. If they still behave like the same dungheads they were last time, people will pick up on that and the alt will receive a fast ban, but if they have truly changed, people will also pick up on that and users tend to accept an alt if they don't make a mess. So, in a way, even if they get the door slammed shut into their face, in a roundabout way, it's still the banned user's choice if they want to stay out and move on, or return (and hopefully be better from that point on). That doesn't really happen with a death penalty.
*returns to Forum Games*