What are the rules in a general work environment if a developer gets slightly violent?
(Emphasis on "slightly")

What happens to that developer in such case?

Um, they get escorted out ...

At least a formal warning, if not summary dismissal; even the slightest violence is not acceptable.

Depends on what you mean.

I get angry and or belligerent sometimes, if things get tense. But not violent. I don't harm or threaten people.

Violence, even "slight," whatever that means, implies something that would not be acceptable in a workplace of almost any kind in my opinion.

My bosses have almost thrown down on each other before. So when I threw a chair once, no one thought it out of the ordinary.

If it's an isolated incident, a good dev will get a stern talking-to. If it happens regularly, anybody oughtta get canned.

It depends... My teammate got pissed coding in Swift 3 with Xcode 8 and started using the Mac keyboard little violently. I could do nothing but just empathise