Actually, in terms of any information that Cohen has that is subject to solicitor-client privilege, his loyalty absolutely has to be to his client. Solicitor-client privilege is a bedrock of the Common Law legal system. If Donald Trump told a lawyer that “I received $1 billion from Putin that is sitting in a Swiss bank”, the lawyer would never be able to reveal that information. My concern is not anything that the President has done, but on whether a weasel like Cohen will fabricate something to save himself from his own personal wrongdoing.
That's one reason why we have a fifth amendment, so weasels won't need to fabricate.