If he had no personal harm and is just some sort of anti-capitalist vigilante that is crazy.
That said, I read the AVERAGE denial rate in health insurance is 17%. Amazing. Of course, that likely includes many legit denials (such as electives, attempted fraud, and stuff that isn't actually covered).
But United was more than double that rate at 35%! And they're the largest insurer in the country.
Which seems absurd. The flip side is they only make 7-8% operating margin, which still seems about double the industry average. Now, on almost $400B in revenue, that extra 4% equates to $16B!
Anyway, among many things broken in the industry, it seems maybe our health insurance costs are too low (ignoring other issues) such that if United denied only 17% of claims they probably lose money. Insurers also really stick it to the small, independent hospitals on reimbursement, which is another grossly broken aspect of healthcare.