Private property involves the threat of violence

This guy says so, by reference to that story about a man forcibly taken out of his seat on a flight.

Of course, he is right.

But by the same token taxes are sums of money extracted under threat of violence.  The threat of violence is what lies at the root of state power. There is nothing specifically capitalist about this. Capitalism is the system that puts the state's coercive and violent power in the service of private property. Communism puts the state's coercive and violent power in the service of state-owned (or, if you insist, communally-owned) property. Even if we abolish property of any kind, so long as the state remains, with its monopoly of the legitimate use of violence, whatever ideological system governs the polity is ultimately underpinned by the threat of violence.

The headline is 'Capitalism is Violence'. Yup, but by the same reasoning, even in late capitalist societies, so are all kinds of other things that the writer presumably approves of, such not discriminating on grounds of race, not abusing children and not polluting the environment. If there's a law about it then ultimately there is the power of the state, with all its police, prisons and guns,  to back it up. 'Environmentalism is Violence too'.