Throwing the controller is a very stupid act, but people are liable to do stupid things all the time, and I think in comparison throwing the controller at the ground in frustration is pretty forgivable. I mean, I doubt MDZ threw a tantrum or started screaming at the guy he lost to. Sometimes when the pressure and frustration is too much though, a guy gets angry and he needs to let out somehow.
Sadly, controllers are the perfect target for frustration vents. They're easy to throw, won't hit you back, and is right within reach of furious, sweaty, and shaking hands. I know it's a stupid thing to throw your controller and I'm sure a lot of other people know this too, but really, it's not something to drop all respect for someone over.
MDZ, you did something stupid, but that's okay, just don't do it again. See? Not hard.