Requirement: Option to disable assistance
Dota 2 has this feature specifically to prevent team griefing. A hero called Bane has the ability to put an enemy or an ally to sleep for 7 seconds, and anyone that attacks that target gets put to sleep instead.
You can see how someone can troll with this.
Tahm Kench is no exception. We need a way to DISABLE him from targetting allies and spitting them into towers.