A lot of Grey Knights players, at my FLGS and in other places, have been getting a lot of heat lately.
More heat than Space Wolves got when Razorspam hit the tables. Maybe a little more heat than when IG brought Leafblower.
In my opinion, yes, they do deserve the hate. When a GK player brings a competitive list (or really, any list in my opinion) it saps the fun out of the game. They have so many defenses against all types of firepower, and then have such a powerful fist behind that that it's very difficult to actually enjoy a game. It becomes frustrating just to focus fire on a single squad just to wipe it out, and forget about destroying a squad of Paladins completely.
But let's extend the discussion here. Why do you not like Grey Knights?
Why do you *like* Grey Knights, if you play them? What is the motivation for you? Is it just because they're an easy point-and-click army or do you like the idea of crushing the will of your opponent even in casual games, or do you just like to have an easy time painting models with a drybrush and chainmail? (Of course, I'm not saying all Grey Knight players are like this, but from polling my FLGS, these are the reasons I've gotten for liking Grey Knights).
I for one don't like them because of how not fun they are to play against. I even traded armies with a friend just to show him how not fun they are! His GK Paladins versus my then-Venom Spam DE. When the games were done, he promptly turned around and sold his GK army and started to invest in Necron (I'm not entirely sure if that was because they were the army of the month, or because he was actually a mature individual).
Let's see how much rage GK has actually generated over the past year.