Taking something that’s not yours without asking is wrong I’m amazed anyone would disagree. But fair enough I am just old fashioned and too strict.
No not at all, what you are is an overbearing bully who can’t deal proportionately with a childs actions. I know this because I’ve been exactly the same myself in the past with my kids . I applaud your values but sometimes you do need to look at your actions from a distance, I’m pretty ashamed about how I’ve behaved in the past, time to sit down with him, apologise for how you dealt with it and then explain calmly why he was wrong.
If that doesn’t work force him to eat tube after tube of pringles till he throws up. 🙂