That alone should be grounds for immediate dismissal. No US military officer can seize authority from the president and call the commanding general of our greatest global rival and tell that general that he’ll be given advance warning of military action ordered by the president. Such an act is dangerously close to treason, as Senator Marco Rubio and others have noted.
The US is not a military junta; it is a republic led by elected civilian leaders, and it cannot allow the creation of any precedent, large or small, of military insubordination.