When is it appropriate to physically attack someone?

Many points really.

The first is the self confidence that comes with knowing you can and likely will win most fights. I am not sure if you ever watched The Avengers but a character speaking to Bruce Banner put it well when she said "Here we are in a room full of people dying to get in the fight - and then there is you who knows he will win just about all of them and he wants only to avoid them". Many of the people I see getting into fights do not know how to fight let alone win. Their ego demands that they fight therefore. Like Bruce Banner however knowing with deep certainty that I likely will - means I do not need to. I have nothing to prove to myself - to them - or my partners.

The second is fear and safety though. As I said my first move in any such situation is to get out, back down, retreat. Get myself and anyone I care about to safety. But is that always possible? I need to know that should I ever get into a situation I can not get out of - that I am ready to deal with it. Much like the americans when they talk about defending their gun ownership. Often they use the line "better to have it and never need it - then once need it and not have it".

The third though is the sheer level of physical, mental, and emotional health studying martial arts has brought to my life. As well as discipline and humility. I remember my first days at Brazilian Jujitsu for example and trust me there is a lot of humility to be found in being put sparring against a teen age girl as a grown man and for that little girl to proceed to essentially turn you into a rag doll that she can do anything to and you can pretty much do nothing to stop it.

You say most of the fights you got into were for your ego's sake? That would be the point I was making in the post you replied to. My ego has no such need any more. And the more I become capable of fighting (I don't think I will ever stop learning or reach a point I feel I am done) the less my ego has any power over me or my decisions.

So no. Violence will always be the last approach for me in any context. I can use it if it is needed. But it will always be the last resort. In defending myself. In defending my ego. In parenting. In anything really. Violence comes last. But if it comes - I can bring it.

I can't see anything in that list moving me to turn to violence. I can't even think why it might. Though at the same time phrases like "crossing the line" and "putting it up to you" are quite vague. So I guess context really is everything on the specifics of what any of those actually mean.

But the middle one - simple name calling directed towards me or anyone around me - certainly would not move me personally to violence.