You can track it all back to when Melbourne was the envy of the league in the 60s. Working class supporters in Collingwood, Richmond, in the West, South East etc used to despise the "toffs" of Melbourne. Some in the media would have been brought up to have a lingering bitterness aimed at Melbourne. Where Collingwood and Carlton supporters genuinely hate each other and have a genuine rivalry, Melbourne is hated by those same supporters purely in a historically class-divided sense. It's a sort of "eat the rich" narrative. It's less directed at the club itself and more at what the club symbolises which traditionally has been the, shall we say, more fortuate suppoer demographics.
Love or hate him it's very important we have the likes of Gary Lyon to flex for us.