Socialism inevitably leads to destitution and famine in direct proportion to the thoroughness with which it is applied. This has been shown to be true historically, with or without Marxist ideology or 20th century totalitarianism. It has starved 17th century colonists in Virginia and Plymouth just as thoroughly as it did Russian peasants under Lenin. It has also been shown to be true theoretically, from Aristotle's elucidation of the free rider problem to Ludwig von Mises's insight regarding the impossibility of the efficient allocation of resources without prices set by a market for capital goods. Socialism, because it is a revolt against human nature, is a genocidal philosophy.
But that is just the consequentialist consideration. Socialism is evil on a deeper level as well. Socialism is evil to anyone with a conscience normal enough to feel in his heart that stealing is wrong and a mind consistent enough to apply that moral tenet to everyone equally.