I don't hate everything Matt Ward has ever written be default because he wrote it, I read the new stories and rules, scratch my head going "who the hell…" then find they were Ward's. He has earned my dislike, because he somehow managed to score the role that Gav Thorpe managed to maintain with about as much wisdom as I've ever seen. Gav Thorpe made many changes to the stories over the years, but he did so predominantly* by adding to the history, not doing a 180 and saying "Nuh-uh, wouldn't it be cool if this fan-favourite chapter of incorruptible super-heroes made invulnerable to the lure of chaos by rigorous training and as much ritual and faith as it is possible to have and instead have it be due to a cheap gimmick involving the sacrifice of the only female body of the Imperium to be truly heroic."
They were incorruptible back when they didn't bathe in blood, for you who continue to bring that up. I agree that they are no longer, and as a result will not be purchasing anything Grey Knights related until they bring back the chapter I love.
As an example of Matt ward's stuff that I don't hate, his new Necrons. He hasn't changed the Necrons from what they were, he added new Necrons to enhance the flavour and storyline potential of the race. While it isn't all great, love the initiative and potential opened up by this move. So, amidst the sea of "Goddamnit" I send a floating bottle contain the burnt and torn scrap of parchment bearing the words "Nice one."