... or resign.

There are lots of instances in professional services where you simply have to say 'no'. If you're not willing or able to represent your client in the way they want to be represented, the correct response is, "I'm sorry, but I'll be unable to continue to advise and represent you on this matter."

In the doctor example above, the doctor will—and should—absolutely refuse to follow your instructions to cut off your arm. (If you are insistent, you can probably find someone in the body modification community to do it for you, though a) it's probably illegal for them to do so and b) don't confuse that with legitimate medical intervention.)