Not empirical. Personal experience is merely anecdotal, and does not support any claim about anything really.
That's not evidence that it has desensitized you to violence however. If after playing that game, someone in real life walks up and stabs someone in the eye right in front of you and you don't notice, then that would be desensitization. About the only observation I could make is that a gruesome scene, set in a fictional fantasy world, no longer bothers you. If anything, I would probably make an inference that you are interpret the difference between fantasy and reality. He also talks about this in one of his later points.
I personally went through Resident Evil 2, curious about all the violent ways I could blow away zombies. I still try to avoid hitting a gopher on the road when I drive to work. Furthermore, the fact that someone plays Manhunt with the goal of getting the most gory kills is not evidence that playing it leads to aggression. It's just a correlation. You cannot conclusively say that getting the most gory kills is NOT because they are already an inherently aggressive person, or have some sort of other, confounding variable.
Then why state that the professor was "wrong." You just flat out said that he was incorrect.