Marx's beef with capitalism was not that capitalists paid too little tax. Instead, it was that capitalists had power over workers by virtue of capital being scarce and labour relatively abdundant. This power advantage enables capital as a class to exploit labour as a class, and to impose lousy working conditions - or, if you prefer, worse conditions upon workers than we'd see in more egalitarian forms of production.
However, I don't see that higher taxes are anything like sufficient to address these problems.
Chris is right to say that:
[The rich's] experience matters and shapes public policy, that of an unemployed teenager in the North East doesn’t: we need to shift the balance of voice in favour of the unemployed teenager and against the City trader.
But I don't see how a tax rise will solve this. Sure, it might at the margin reduce the ability of the rich to buy politicians. But this isn't the only (or even main) route through which capitalists exercise power. They do so partly because of our "disposition to admire, and almost to worship, the rich and the powerful", which causes us to fail to see that "The skills required to succeed within a spontaneous order are little connected to the skills needed to understand it.": how often does the BBC invite a businessmen to talk about the economy and economic policy as if he were an expert? And it's also because capitalists' control of investment allows them to appeal to "business confidence" to resist any policies they dislike.
Higher taxes won't solve these problems. Nor will they solve the fundamental problem that workers lack access to scarce capital. Indeed, if they cause an "investment strike" or migration of entrepreneurs, they might even worsen the capital scarcity.
By all means disagree with Chris, or agree with him. You cannot, however, call that piece Marxist. I fear Jackart is making the common rightist mistake of using Marxism to mean "really nasty leftism", when in fact Marxism is in many ways different from mere social democracy*.
There is, though, something in all this I find depressing. Marx thought that the overthrow of capitalism - which he saw as a liberating process - required not the intervention of a technocratic state, but rather the action of workers themselves: this is partly because, to him, the capitalist state was a "committee for managing the common affairs of the whole bourgeoisie". However, we have now lost the idea or even perhaps hope that workers can be political agents in themselves. It seems instead that political agency lies only with the rich or the state. And I for one lament this.
* Let's leave aside Jackart's belief that Marxism is "evil". Many Marxists opposed Stalinism, and paid a higher price for doing so than western cold warriors. The offer I made here stands: if he doesn't accuse me of liquidating the kulaks, I'll not accuse him of murdering Alan Turing.