Let's not get off track. As a community of disciplined, respectable airsoft enthusiasts, we can't afford to be divided amongst each other.
Without one person claiming airsoft's realism is something empirical like "a 6 out of 10" when compared to real combat scenarios, both sides are just arguing pointlessly without aim.
I'm not arguing either side, but airsoft, which already pushes the limits of safety, does help with "stress inoculation". In paraphrasing Lt. Col Dave Grossman's "The Bullet Proof Mind":
Sprinting to get your heart rate up to 175 bpm and taking a few target shots is not the same as when your mid brain takes over and guides your survival when the targets can shoot BACK at you, which you cannot safely do with real combat situations.