Well, taxation has the threat of violence, in that if you don't pay your taxes you will eventually be caught and sentenced to jail for tax evasion

Yeah, I understand the logic behind it, but still most people would not include "taxation" within their definition of "violence". Many people would consider taxation by a democratically elected government to be legitimate; people may not like it, but they don't consider it an act of violence. And it's worth noting that that libertarian definition does not consider it "violence" to, say, have someone arrested for violating a contract, or for theft, ect.

Basically, the word is being used in a non-standard way that hides a number of assumptions that not everyone would necessarily agree with. I tend to think it's better to clearly lay out what your assumptions are and how you came to them when making an argument.