This Is From the ToS

Inappropriate Behavior
Our Definition of Inappropriate Behavior
Disturbances that do not fall under the harassment category but are intended to prevent or hinder game play for others are considered inappropriate.

I would say what the Tank did fell under this. Though this would be subject to how the GM interprets it since their policies are not that well defined but definitely see this as going against the user agreement. GM, if was able at the time should have sent the offending tank and told him to play well with others or leave the group. FFXI GMs have been known to put people in the white room in FFXI for the most asinine reasons. Since this is new launch should make their presence known, jail a few people for doing dumb shit so people play nice.