No, they should have their license revoked. Those people are not doctors, they are opportunistic capitalists in the medical sector that should have no right to practise medicine.
In fact, this scheme could only work if doctors complied. I would say what they did was much worse than what the billionaire did. They're bad actors.
http://edition.cnn.com/2016/08/25/health/us-surgeon-general-...
This makes you wonder how many professors at medical schools also go on nice holidays paid for by pharma companies or lobbyists.
You can’t change these incentives without moving the US to a nationalized health care system, including public financing of education for doctors and much harsher regulation of the pharma industry. As long as you have doctors going into massive amounts of debt to finance their education and a drug industry with obscene wealth and power, you’re always going to arrive at this outcome. Capitalism is fundamentally opportunistic, which is why it has no business in healthcare.