griefing is against ToS.
Behavior that intentionally detracts from others’ enjoyment (such as griefing, throwing, feeding, etc.) is unacceptable. We expect our players to treat each other with respect and promote an enjoyable environment. Acceptable behavior is determined by player reports and Blizzard’s decision, and violating these guidelines will result in account and gameplay restrictions.
While we encourage you to report players that are behaving in a disrespectful manner, falsely reporting another player with the sole intent of restricting their gameplay is also unacceptable and will result in penalties to your account.