Most people doing their job quite literally are just doing their job, trying to make it to the end of the day. Believe me, even people in hr love their children, worry about the future, worry about their job, have hopes, fears and dreams and have to contend with shitty bosses.
Can you imagine one day the CEO coming in with a list of people that YOU have to fire, that YOU have to face, that will cry and yell in front of you as if you're the one who did this to them?
Most people are pretty okay, actually, and not remotely evil. They might do bad things because they're pressured or feel pressured, most people don't enjoy firing others.
I get your point, but in practice It's not that easy. If you have a family that depends on you, you'd pmbe surprised what you're willing to do not to lose your job.
The HR person who works with my team actually said "I actually really like firing people. Well, that didn't sound right... but I do like making these changes."