Meh, that is not a critique of Corbyn as a Marxist, it's using communism as a scare word without delving into what Marxism actually is and why Corbyn matches the definition. Do you have a critique by someone who actually knows what Marxism is?
I can find plenty of descriptions of many politicians as Fascist (and usually better researched than this), doesn't mean most of them are.
Specifically that article is by Damian McBride, who was Gordon Brown's SPAD. It's continuation of a political brawl by means of a newspaper column. Not a very nice chap:
"On 11 April 2009, he resigned his position after it emerged on a political blog that he and another Labour Party advisor, Derek Draper, had exchanged emails discussing the possibility of disseminating rumours McBride had fabricated about the private lives of some Conservative Party politicians and their spouses. The emails from McBride had been sent from his No. 10 Downing Street email account."
I can find plenty of descriptions of many politicians as Fascist (and usually better researched than this), doesn't mean most of them are.