No it is probably not ethical per se but it is often done. Obviously it's easier if you have a company lawyer. But if you don't have one then I don't see any major problem with looking at other company's' privacy policies and using them as the basis for your own. I would never copy someone else's material verbatim but this process has been going on since before the Internet.
Regarding a duplicate content penalty, why would you be concerned about this on a PP page?