If you only told him to shut up, you shouldn't have been punished at all haha. If you're not lying in your report then it's on whoever punished you.
Telling someone to "shut up,"especially after they tell you they'll rip your valuable items (threat), is not an insult nor lack of respect. However, you were punished for "death threats" too.. you kinda turned that part on yourself. For sure though, just saying shut up isn't disrespect by definition. How you acted after was more important to the punishment.