"regardless of how others are behaving"

So?

If the implicit assumption is something along the lines of "people I disapprove of deserve what's coming to them", then again, that interpretation is entirely yours.

How is that the same as "Please don't make personal attacks here, even if they deserve it"?

It's not at all required to mention if you disapprove of something when chastising someone for abuse. It undermines the point. Makes it sound like some unfortunate technicality or point of honour.

If you have a problem with the content of the thread, mention it, and defend that opinion. Otherwise, don't mention it. Flinging labels from above helps nothing.