It's of great practical importance. There's a big assumption that you're making here, in that all dialogue is or promotes rational dialogue. You at least strongly imply this by imploring that RIP warrior not be banned so that you can attempt to ''reason'' with him if you wish. But what if what someone is saying had the effect of derailing rational dialogue, even if you agreed with it?
Let's say that I didn't like black people, and wanted to come here to rationally advance my views that they're just no good. I might post a study by JP Rushton or Arthur Jensen. Many people have done so here over the years, and not been banned for so doing. But then RIP comes along and never rationally argues about anything, and instead posts invective against black people (whom in this hypothetical I don't like) that completely derails the conversation? I would support him being banned.
Now, why did you do that? Why do you get a criterion beyond disagreement, but your interlocutors don't?
Why is it that whatever is disruptive about spam (volume) cannot be also disruptive about the content of certain posts? This requires a lot of fleshing out, IMO.
Here's what I'm referring to with ''cannot be meaningfully agreed or disagreed with": jews are maggots in the rotting corpse of germany. It's a metaphor, jews are literally not maggots, and germany is not literally a rotting corpse. As such it is contentless invective designed to short circuit rational dialogue, and interact with the base animus of certain people. It is an aesthetic judgement against which you can say ''no,'' and the author of the statement can say ''yes'' and that will be that. The content free nature of the statement is the point, in fact.
You didn't, but you did ascribe to me something I didn't say either, so here we are.
You shouldn't rely on the philosophical commitment of others, either in a negative or positive sense. In the one sense, they will always let you down. In the other, they may just decide to surprise you.