From the ToS:
Ruling out meta-discussion, including ruling out arguing against the person, can open the door widely to propaganda and to irresponsible behavior, and to everything that comes with them.2. Speech
Any subject matter that may be off-topic or is intended to cause disruption or harm may be removed without notice. This includes, but is not restricted to:
e. Disruptive meta-discussion (i.e. discussion about discussion, including in-topic complaints about the existence of discussions that don't suit your preferences)
If no meta-discussion is allowed, then people can promote views they don't hold, criticize others for not holding those views -- and nothing can be done against that according to the ToS.
Note that not every ad hominem is automatically fallacious:
This becomes especially relevant when it comes to moral issues discussed in religious/spiritual circles. Ruling out all arguing against the person means that people can promote moral views they don't actually hold, and they get to criticize and even severely judge others for not holding those views -- and they can do so with impunity.Non-fallacious reasoning
When a statement is challenged by making an ad hominem attack on its author, it is important to draw a distinction between whether the statement in question was an argument or a statement of fact (testimony). In the latter case the issues of the credibility of the person making the statement may be crucial.
Criticism as a fallacy
Doug Walton, Canadian academic and author, has argued that ad hominem reasoning is not always fallacious, and that in some instances, questions of personal conduct, character, motives, etc., are legitimate and relevant to the issue, as when it directly involves hypocrisy, or actions contradicting the subject's words.
The philosopher Charles Taylor has argued that ad hominem reasoning (discussing facts about the speaker or author relative to the value of his statements) is essential to understanding certain moral issues due to the connection between individual persons and morality (or moral claims), and contrasts this sort of reasoning with the apodictic reasoning (involving facts beyond dispute or clearly established) of philosophical naturalism.
So someone, for example, can be a warrior for compassion and tolerance, yet exhibit none themselves when in actual conversations with others.
And we're supposed to just okay this?
Do you really want to support this??