Yes it is. Look at KyR speedy, he gets banned all the time for griefing.
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[u]Griefing[/u]. Not moving players that aren't even playing and accidentally causing their death. You can't prove otherwise. Or should that guy in Crucible, who moved in your way and blocked your shot and caused your death, get banned too? Logic. Using that logic, any AFC player should be banned because they cause others to die since they won't help. In other words, griefing.