I think there's a moral component and a practical component. The latter becomes very difficult when taking a stand against a government entity in your home jurisdiction, since the offending government may put you out of business or something.
For example, in Nazi Germany (which I agree is a useful example to reference), a company that refused service to the Nazis would have had its executives murdered and been taken over by the state within a day. (My guess based on my recent read of The Rise and Fall of the Third Reich, but I may be off).
On the other hand, refusing service to North Korea (sanctions aside) is a clearly ethically correct thing and offers little practical risk for companies based in the West.