Yes, John Brennan made the right call in publicly condemning Donald Trump's policies. Mr. Brennan recently informed Donald Trump of the folly in cancelling the deal that the United States made with Iran. This deal has kept both of our countries safe and has improved the safety of our allies in the Middle East.
His statement was important, not only so that he can save face once all hell breaks loose, but so that other people can hear and understand why Trump's policies are bad. While it might be too late to stop Trump from being president, we can work together and reduce the effectiveness of his policies.
While some of the policies that Trump has discussed would affect members of the CIA, it shouldn't have been something that the director of an organization that is famed for its secrets to publicly address. It just stirs up that masses against the President-elect. He should have talked privately with Trump on the matter instead of the manner that he had taken.
As long as Brennan is still a member of the administration he should keep quite about his thoughts regarding Mr. Trump. Mr. Brennan is not helping anyone other than himself by condemning Mr. Trump publicly. It is the obligation of the Executive Branch and the people that work there to ensure that there is a smooth transfer of power. Once he steps down, he can condemn Mr. Trump and his policies all he wants.