That's because there's no direct link between being conditioned to kill, and actually killing. That's the classic mistake that is made, and which I pointed out in my post, and which you ignored.
You haven't explained any practical basis for your "conditioning to kill" assertion, or even what exactly that's supposed to mean.
This is entirely true, but this is precisely why it's conditioning. Soldiers on the gun range can shoot at their targets for exactly the same reason - they know it's not real. Yet nonetheless, it's conditioning them to kill.
No, it doesn't "condition" them to kill. It teaches them useful weapon-handling, target-aquisition, and reaction skills.
Conditioning is a much more complex process that involves classroom instruction in rudimentary philosophy, and the creation of a culture which supports desirable traits, while punishing or minimizing undesirable ones.
The vital element of conditioning is that the environment must match actual killing as closely as possible, while still avoiding a level of realism that would cause psychological trauma.
Actually, that's not entirely accurate, and based on somewhat outdated beliefs. Far more important to battlefield conditioning is creating an appropriate culture and supportive environment. Replicating a battlefield is good for testing skills and responses to stress; but group identity and peer support is a far more important factor in instilling the ability to kill an enemy while minimizing disabling psychological backlash.
In fact, there is very little actual realism in training; but there is a great deal of emotional stress, even trauma. None of it is associated with the battlefield, not because of the potiential for causing trauma; but because to do so would not effectively produce the mindset necessary.
The point of conditioning soldiers is to allow them to perform their duties with a minimum of psychological backlash. In order to do that, they need a resource for minimizing the psychological effects of performing their duty. Doing so requires creating a culture in which a soldier can be fully immersed. Strong psychological stresses are induced through various means, but only in very controlled settings which encourage a trainee to rely for support upon his peers, rather than himself or his superiors. In fact, superiors are intentionally placed in the role of "enemy" during these exercises. The trainee is completely isolated from every traditional means of support save for his immediate peer group. And just as the peer group is made the means of support, it is also made the means of punishment of undesirable behaviour, further reinforcing the group reliance and "us vs them" exclusionary behaviour.
It is this conditioning, basically a form of controlled and focussed mob mentality, that allows a soldier to kill enemy combatants without overwhelming psychological trauma. It's the same peer-reinforcement mentality that enables uncontrolled mobs to engage in lynching, gay bashing, gang rape, and other forms of violence without compunction or significant backlash; controlled by a strict discipline and code of ethics. That discipline can break down, and result in tragedies like My Lai and Nanjing; which shows just how close the two forms of group reinforcement are. Law enforcement officers go through a similar, but greatly reduced, variant of this training, with more emphasis on individual action; thus possessing a greater risk of psychological trauma.
Battlefield conditions are almost completely irrelevant to the process; and making them too realistic is counterproductive insofar as they make a soldier more likely to be self-reliant instead of group-reliant.
You want an environment that closely replicates the fundamental mechanics of the battlefield, in a less emotional and immediate way.
This is useful, but only to a very limited degree; and cannot even remotely accomplish the desired conditioning. All a battlefield environment can do is teach soldiers how to perform within that particular environment. As previously noted, it can even be counterproductive.
So, for example, targets appear randomly and unexpectedly, and when you achieve a successful "hit" those targets disappear. That's what modern military gun ranges do, and that's what computer games do.
That's what nearly every shooting game in the history of shooting has done; from military training down to carnival games. It is useful for developing skills; not useful for developing the ability to kill without crippling psychological backlash.
Arguably computer games do it better because the "fantasy" aspect of watching 2D images separates the shooter from the action enough that you can more closely replicate the mechanics of killing without issues. If targets on the gun range moved about like people, bled, writhed on the ground when shot, and screamed, I would be willing to bet soldiers wouldn't be able to work the range. It would traumatise them.
Only if they were unable to dissociate the fantasy game from reality; which is extremely rare for those who are not mentally ill. Stable, rational people don't walk out of
Saving Private Ryan emotionaly traumatized; because they know that it's not real, it's fantasy (children and the mentally ill who have difficulty dissociating fantasy from reality are a different matter). The same with soldiers in training. No matter how realistic you make the training, as long as the soldier knows it's not real, there is no significant long-term psychological impact.
In contrast you can have all of that happen in a computer game without the least trauma or concern.
Which is why it's been proven effectively useless for anything other than skills training.