Because the degree of responsibility is far less. The UHC CEO was personally responsible for the deaths and suffering of many thousands of people so as to enrich himself and his investors.

He wasn't just one more cog in a system that de-emphasizes human well being in favor of profit. He was in charge of just how far to turn the dial of profit > human well-being. Nobody was forcing him. It was all discretion.

Sometimes people figure out ways to engage in intensely antisocial, self-serving behavior that falls into a loophole that shields them from legal consequences.

We can recognize that the better thing to do is change the laws than become vigilantes. On the other hand, we can also recognize exploitative behavior and temper our displeasure with vigilantism with relief that it seems like overall people are better off.

That's most of what I see. People aren't saying, "Wow, we should run round killing CEOs, health care workers, and so on, left and right!" They're saying, "This individual was one of the worst of the worst, and I'm honestly glad they don't have the opportunity to cause more harm in the world."

That is, I think the position usually starts off more sophisticated than what you call "second order thinking".