I actually think he's right in terms of Presidential actions, or you could end up potential criminalizing policy decisions. So for example, suppose it wasn't a political rival but some foreign leader who was killed, and some prosecutor somewhere decides to prosecute the President for murder? There has to be absolute immunity for official acts unless there is first an impeachment and removal from office.
But the all caps thing....I'm just sick of his sixth-grader mindset and behavior.