I don't think I said anything about the law.
In the end, for someone like me, that's all there is to it: am I going to "get away" with this, or are they going to put me in jail
Nope. Nothing in there about the law. But from what you've said, the law agrees with me. There is no physical response to words. A physical response is justified only when there is reason to believe that the person is going to do something other than talk.
So what is it, exactly, that you're disagreeing with? I'm pretty sure you're not saying that you think it's ok to smack someone for words alone, when you have no reason to think they're going to do anything other than talk.
I think it's ok to smack someone for words alone, provided that one has perceived an actual and credible threat in those words, and that a "reasonable person" (that's the legal term) would recognize and respond to that threat in that way.
I have no other measure for when it's okay, but under those circumstances, it's ok.