In fact, it's theft, and its modern stalking horse "social justice" is theft as well. There certainly are mechanisms through which a surplus may be voluntarily contributed to the collective - charity is far older than Marxism, and it's good for the soul that the Marxist denies we have. But the flip side of "to each according to his need" is "from each according to his ability", not according to his willingness to share. The socialist state will provide that motivation at the point of a bayonet. The more productive will always be the slave of the lesser, and the ultimate master will be the one who produces nothing at all. Why anyone would ever think that system would work in spite of a century of contraindicative evidence is quite beyond me.
Well said.