We aren't...and the guy was too much of a pansy to pony up the truth. Sucks to suck....he lived a helluva lot longer than anyone he shoved into an oven. Not crying a river at all. He can reap what he has sown.
And yet, they stood in towers and watched people going into what they knew were gas chambers. They watched bodies being shoveled into crematoriums. They knew what was going on. The fact that many of them tried to save people on occasion shows that many of them experienced some degree of guilt. How could they justify to themselves standing by and letting millions more die?
Maybe they figured that they there was nothing else they could do. Maybe they figured they'd be killed themselves. But if you're life consists of patrolling the perimeter of a mass-slaughter camp, if that a life worth living? I suppose there wasn't much they could do and keep their own necks, but does that matter?
I'm not fond of putting myself in a theoretical situation and predicting my reaction to said situation, but I'm positive I could not have stood guarding a concentration camp. Better to die yourself and be done with it than live and think about what you are doing.