Can type 1 diabetes cause really bad anger outbursts?

No, Possibly Reverse. As embodied souls, mind, emotions & brain control body, millions of signals/sec, with corresponding feedback. Thus, though complex, the opposite is a bit more likely. While someone with type 1 might be appreciative that a hormone they are no longer able to manufacture is available to help them stay alive; they are also likely to find monitoring & adjusting frequent injections a pain; promote anger.