George Monbiot is left wing, but that doesn’t inherently make his viewpoint always incorrect and without merit and you can’t be looking very far if you think there aren’t journalists who can’t be said to be more left wing than him.
Owen Jones, Ellie Mae O’Haegan, Ben Norton, Aaron Bastani, Matt Zarb-Cousins and Max Blumenthal are just a few off the top of my head. There was a fuss in the Corbynite sphere last year when they decided Monbiot was an evil Blairite red Tory because he was deemed not lefty enough.