No modern country says 'We're going to have an unethical foreign policy'. It was the UK government's actual announcement that theirs would be ethical which sets it apart. Former US president Jimmy Carter may well commiserate with those in Whitehall. In the wake of the Vietnam conflict his administration tried to publicly push human rights to the top of its agenda. It proved a difficult task.
Every government thinks it's smarter than the ones that came before.
Governments don't start in a vacuum. They inherit policies. Certain policies, if already in train, are not easy to pull the plug on. These often conflicting considerations have caused much debate between cabinet ministers. The ban on supplying arms to the military rulers in Pakistan has been lifted.