Those threats are very different to threats of violence/theft.
"Do what I want or I will walk away" is not a threat of physical harm - it's not nearly like the one I mentioned.
In a healthy world countries should be competing for businesses and wealthy individuals to take up residence and taxation should be a part of that equation.
I understand, of course, that there is a need for those of us who can to provide for those who cannot (I stress cannot as an absolute, it may never be confused with will not, might not, don't fancy it, etc). I absolutely believe though, that the incentive to work must be kept at a premium and there needs to be a significant gap between working life and not working life to ensure that incentive remains.
I also believe heavily in altruism and the positive effect it has on society. None of that, however justifies me giving away half of everything I earn to the tax man - it's just preposterous.
Imagine a clean slate, imagine taxation has never existed and the socialist ratchet has yet to get its filthy claws into my wallet. Then try to imagine a working, sensible tax system. I'll bet giving away half of one's earnings, money I could otherwise be spending on my son, is not in that system - it's just ridiculous.
A non-violent way for people without economic clout to negotiate with those with all the power is collective bargaining, but you are against that. When the lower orders threaten to withdraw their labour it's extortion, when rich individuals or big companies threaten to withdraw their money, that's just good business.
You would pay less tax if those above you in the economic food chain paid their fair share, rather than hoard all their wealth off-shore. Why don't we start there and then fix the rest afterwards? The right wingers prefer to start on those with the least money first, then the state and then...never touch the wealthy.