There's the rub. For so many Marxists, questioning Marx is like questioning God. Yet, one of the most important things Marx ever wrote is not applied to Marx himself, "question everything!" Marx himself wrote that his earlier writings had been superseded by time. In his introduction to the Communist Manifesto in 1873, he wrote that much of the Manifesto was obsolete, but that as it was an historical document, he had no right to change it. Given that it was a programmatic statement of an actual political organization, Marx is correct, but it would have been nice for him to do it anyway. No one remembers the Communist League anymore. Everyone still knows who Marx was.