"if they fundamentally disagree with the president’s principles, and they wish to condemn them rather than persuade him, they should resign and go to work for somebody’s campaign."

Daniel McCarthy writes at the National Interest,

Americans may be under the impression that the president they elect is the man who directs the country’s foreign policy and sets its immigration rules. But a thousand or so officials in the State Department are of a different opinion. They have put their names to a cable registering official dissent in protest against President Trump’s executive order that bans most travelers from seven terrorism trouble spots—Syria, Libya, Iraq, Iran, Sudan, Somalia and Yemen—from entering the United States. But the dissenting diplomats go far beyond merely criticizing the order: they play politics and attack the very principles behind the president’s immigration policy. Indeed, they substitute their worldview for his.

...if they fundamentally disagree with the president’s principles, and they wish to condemn them rather than persuade him, they should resign and go to work for somebody’s campaign.

Read more here.