Yes, you can. You can not buy their products or services. With insurance, it's a bit harder, but there are options. Lobby your employer to switch providers. In a couple, choose the other's insurance. Or quit employer provided service entirely and buy it on the exchange. "Oh, but it's more expensive!" you'll say. Well, you get what you pay for. It's not United Healthcare's job to make it easy or cheap for you to switch from their plan to someone else's. Don't choose to do business with cut-rate shady companies whose reputations are well known and then act like it's your divine right to gun down the CEO.
There is a chasm between understanding (and experiencing) the frustrations of the millions of folks who've been bad done by insurers and believing in a "divine right to gun down the CEO." I don't see anyone here advocating that.
So, let's talk about lobbying employers. Are you shocked to learn that C-Suite folks often get certain personal benefits from choosing one company over another? Look at all the companies with truly crappy 401K investment choices with high fees. That's changing, because the law changed, but it was (and likely still is) a reality. Magically, the C-Suite folks often got benefits, and the brokers who sell the company the plan make bank.
I had the miserable experience of serving on a company's team for determining our 3-year health insurance buy. This was before Obamacare, FWIW. The company had about 1000 employees, with about 700 in one state and the rest spread around 8 different states and the DC/Maryland/Virginia area, considered partially experience rated. We used a broker to identify options. I'm pretty competent at analysis, but it was like comparing apples to tea kettles to lawnmowers. Basically, other than premium costs and deductibles for in vs out-of-network costs, the rest was like trying to grab handfuls of grape jelly, since the insurers are free to change participating providers, formularies, pre-authorization requirements, and virtually every other aspect. Meanwhile, the CEO and Sr. VPs had a special healthcare benefit that provided for coverage of many items not covered by anyone else's regular plan.
And then--bonus!--the Blue Cross (Anthem) plan we chose turned out to have secret deals that meant that a pregnancy/childbirth experience where they were supposed to cover 90% of the costs (all in-network) actually had them covering substantially less than that because the charges/coverage printed on the EOB didn't match what they paid the providers. I learned about that when I had trouble reconciling a bill and got a printout from the OBG's business manager showing the truthful transactions.
In the end, they paid. Bigly. Because I was one of the lead plaintiffs in a class action lawsuit that cost them millions. I didn't get millions, FWIW...the lawyers were the ones who made bank. But this is the kind of crap insurers pull day in and day out. The rage against insurers is real, and justified, though murder is not. Jail time, on the other hand....