The word moderation is perfectly suitable to the spirit of what you are trying to convey, but it speaks more to the outcome than the means. Yes, we want conversations to be focus and fruitful, but moderation does not speak to how. It seems like your solution is to define a standard of behavior and to then ban/shun anyone that does not uphold to that standard.
My problem with this solution is that it feels too rigid and impersonal. In a community, we get to know the members. We get to understand their personalities. Yes, some of them will be more difficult than others, but we need to allow for the emotional and intellectual range and complexities that, as you pointed, our flawed humanity brings to the table. I am not saying that no one should ever be banned, but what I am saying is that it should be a last resort.
This is why I like the word mediation better. Mediation speaks to the means of how we reach moderation. We should always strive to resolve conflicts in ways that allow all of the involved parties to become better through the struggle.
Very curios to see what your thoughts are around these ideas, and thank you for writing about this. I agree with the feeling that both the do-nothing and do-something positions seem similarly harmful, so we need to struggle with these conversations repeatedly and often.
What constitutes "good" moderation is a whole other topic, and one that I don't have enough expertise to give more than random personal opinions on. (And my random personal opinions would probably piss off a lot of people.) My point here is that just because good moderation is hard (true) doesn't mean we can or should avoid it. Calls for "no moderation" are, almost invariably, born of a desire to not be yourself held accountable for your actions, and even if well-meaning lead to community death.
I didn't say that we should ban/shun anyone that does not uphold a particular standard as a first-step. Sometimes banning people really is the best solution, but it's always better if something else can be done instead. (Education, mediation, timeout, whatever.) If those don't work, though, then removing a toxic element is better than trying to mediate between toxicity and everyone else.
The individuals banned from the PHP Internals list in this case had been sources of trouble for literally years. Their removal was long overdue.