Karl Marx was one of those rare geniuses whose vision is so great and conclusions so fraught with troubling implications for the established order that they are immediately subject to controversy and assault. Marx is a permanent resident in that rare, transcendental pantheon populated by the likes of Galileo... and few others.
135 years after Marx's death Nobel Prize winning economists stumble on the concepts Marx pioneered concerning value, price, and profit. And it's not because they are so difficult to understand. It's because, again, their implications are so profound and revolutionary.
Universally, those that condemn Marx, on one absurd basis or another, do so without having ever read a single word that Karl Marx wrote. They speak from a position of blind prejudice and nothing more. The fact that Marx, Marxism, and Marxist have become the swear words of the abysmally ignorant is not a sign of Marx's lack of relevance in the modern world - but just the opposite. Marx continuously looms as the nemesis of nationalists, racists, and reactionaries of every stripe.
The fact that these very same ignorant souls (some of whom, such as Stalin, dared to call themselves Marxists) are leading the charge into mankind's potential oblivion is the most disturbing fact of them all.