Why destructors should not throw

Is it acceptable for a C++ destructor to throw an exception? Why or why not?

No, avoid it. Destructors run during stack unwinding; if one throws while another exception is already in flight, the program calls std::terminate. Since C++11 destructors are implicitly noexcept, so a throw terminates anyway. Catch and handle errors inside the destructor, or expose a separate close function that can report failure.