Comms, I understand you may feel differently about Grossman's work, more so as you were his student. I also agree that this is not the best place to discuss Grossman's work. If I understand correctly however, you would like some clarification, which is all right and well so I will try to address the issues briefly.
Without going into too much detail regarding PC games and TV desensitization, my main objection, which is shared by a number of people I have worked with, is that desensitization is one thing but teaching actual combat skills is different altogether. A child who plays Counterstrike all the time may pick up some knowledge that is in fact applicable to the real battlefield. Computer simulations have an important place in military training as well but they only have practical value as part of a much bigger system than involves serious training, technical, physical and mental. Real death and killing is much different from computer-generated special effects and you cannot get used to it simply through virtual reality.
What I find more problematic about Grossman's work is his methodology and lack of critical approach. As a military historian by profession and close to my PhD I can see serious flaws in his arguments. Grossman seems to be well in his element when discussing recent warfare and training. But his treatment of earlier conflicts cannot stand up to scrutiny. Even when analyzing WWII he makes repeated arguments based on
(perhaps unintentionally) misinterpreted sources. For example, his claim that only a very small percentage of troops in WWII ever fired their weapon in anger is based on some very unreliable statistical data which is further distorted as the statistics apply not just to combat troops but all kinds of rear-area and support personnel.
Even more disappointing is Grossman's treatment of earlier periods like the Civil War. He does not seem to have a working understanding of the 19th c. tactics and weaponry, let alone a wider grasp of the social context, which is very important as pertaining to recruitment, training etc. Therefore, he draws flawed conclusions based on loosely interpreted facts, e.g. the seemingly poor effect of muzzleloading rifles, many of which were found loaded after the battle. Yet that in fact has little to do with any human aversion to kiling but rather poor training, complicated loading procedures, inherent technical problems of muzzleloading firearms and the overall "fog of war", which was a very real factor before the introduction of smokeless gunpowder.
In my opinion, much of what Grossman has written on the mental aspect of violence holds true. Many of his suggestions for more realistic training methods seem to make good sense and have been proven in practice. But his overall academic approach leaves much to be desired and undermines many of his conclusions, which are sometimes exaggerated, out of context or simply false.
Perhaps you are not aware of the fact that Grossman's On Killing (and to a varying extent his more recent works) have been seriously challenged, so much so that some would call Grossman a controversial author. Again, I appreciate the fact that you respect Grossman as your instructor and no doubt some of the critique directed at him has been unfair. I would suggest a quick Google search so you can get an impression yourself as there is a fair bit of material online. One article that I have bookmarked on my PC can be found here:
http://www.theppsc.org/Grossman/Main-R.htmI hope this answers your question without stirring any more controversy. If you wish to discuss this further, you can drop me a message. Respectfully, Tom