criticize the action

In order to avoid unnecessary escalation of conflicts, and to de-escalate ones already in progress, it is usually preferable to avoid ad hominem criticisms of people. In discussion, it is far more appropriate to criticize the action as dangerous or useless in its context, rather than making blanket accusations against one's character.

In a large public wiki, it is particularly important to avoid ad hominem on profile pages - the wiki equivalent of a direct provocation. Critical accounts of individual behavior are best located on pages named for the incident rather than the person, though the pages can and should be linked from the profile. ''To refactor claims about incidents so they are only summarized on profile pages is one way to achieve this.

Criticizing the action is much easier to defend objectively (did this action "cross the line or not"), while trying to objectively label a person as a "scoundrel", a "liar", a "nasty troll", etc is (short of some kind of operational definitions of who "is" and who "isn't") is generally an exercise in futility.

It should be noted that statements of fact, regardless of the negative connotations, are not criticisms, ad hominems, and whether "derogatory" in a given context or not, remain fair game under reasonable libel laws - note Ontario libel law is an exception. There are however subtle points of order in describing any such actions:

A "convicted drug dealer" is just that, and it is fair to say so, but to be fair and balanced one should not overemphasise minor failings except on pages specific to an incident regarding drug use or trafficking. On the other hand, there exists no such thing as a so-called "convicted pedophile". This is hate speech intended to create a category of person who may be openly despised and whose human rights may be disregarded.

Contrary view: usefulness of trolling