When you join parties you agree to those rules. Going against those rules breaks the "player agreement" clause in the ToS and if can be considered under the "disruption of gameplay" clause as well because if you don't follow with the set rules, like "farm" party causing "wipes" you are disrupting the other players trying to farm
That is jut demonstrably wrong. If you've ever filled out a complaint in game you'd know that a GMod contacts you with in 30 minutes to talk to you directly about the issue. The clause is to stop people like WHM's who just type "lol" in a fight and watch people die because they find it funny. I've talked to GMod about this personally in detail.