It's mostly the fact that it's pretty hyperbolic. There's no doubt the school has a bit of influence, but definitely not to the degree people claim it does. People that go there aren't guaranteed jobs, and the big reason they do get them is with hard work and the fact that the school is 30 minutes away from Burbank. There just so happens to be a few factors why these people get these positions easier than others, which is mainly location. It's like this with every other industry that's centralized in one area.
The thing that gets ridiculous is claiming that everyone that attends does the whole bean-head thing and that only Calarts alum get jobs or can pitch shows. There's a tight knit culture amongst the students and this does transfer over a bit into the job scene, but it's not as cliquey as it used to be or could possibly be. There are plenty of people at large studios that aren't from Calarts, and if anything Calarts alum aren't even in the majority. It's just the big name show runners are because they know how to pitch shows and make their way around the industry because they're more or less taught to pitch from day one.
And that image isn't by a student pissed off by the system. It's a student making fun it. There is no system.