I still own (never play) a vinyl copy of the Sex Pistols' "Never Mind the Bollocks." Mclaren was detournement in action. He was like a spiky-headed version of Elvis' Colonel Parker to Johnny Rotten and Sid Vicious.
Mclaren was a provocateur in the best sense of the word: "one who provokes." He was an intellectual "shit-stirrer." And sometimes the shit needs to be stirred.
It's possible the Punk movement as we know it, would not have existed, and certainly wouldn't have had the same spiky, edgy flavor without McLaren's influence.
One man can make a difference, even if his credo is smashing and mashing up differences.
UPDATE: And of course he was a showman, a promoter extraordinaire! Little Johnny Rotten was the apple of his eye and the whole Pistols thing was a wicked r&r spitball into the cultural stew!