Take a look through the rest of the thread -- the guy is the poster child for why we should actually investigate smears like "he hates Marx" instead of taking them at face value.
I say in Why You Should Be A Socialist that [Marx] had “a better understanding than almost anyone else of the way that economics determines the fabric of the social world,” and praise texts of his as “brilliant” and “profound,” full of “great insight.” I am not sure how that can be squared with thinking I have scant regard for him.
His issue with Marxism (in addition to anarchist critiques of it and the broader ML tradition) is basically that some Marxists are dogmatic almost to a religious degree, and can condescend to people who haven't read Das Kapital in its entirety.