I've got to say that I agree with the assault charge.
The patient did not consent to having any kind of graffiti put into her liver. What the surgeon did is arrogant and crass and showed a disregard for the fact that it was a human being on his operating table.
The article linked to comes across as arrogant too. 'I'm a surgeon, I save lives, it shouldn't be criminal to have a laugh over an unconscious patient'. Actually, how about respecting the patient and adhering to the rules of your profession. You know, act like a professional...
Nurses and other HCPs get hauled over hot coals for this kind of shit, and so they should. Accountability for actions is important. Surgeons should be just as accountable and perhaps should be knocked of their pedestals to remember that they're not god-like. They're doing a job that they're trained for, should behave like professionals and have a modicum of respect for those vulnerable people who are on their operating table.