Given that, as a Flight Safety Officer, I often had trouble getting an MOR out of some Captains within 48 hours, I am quite impressed that the Captain in this case produce such a comprehensive report in such a short time.
As I said before, the Captain's decision in such a case is final. The reasons are irrelevant. He is the final responsible authority for the safety of the aircraft, its crew and all passengers on board. He made a decision. It is not up to the courts to challenge that decision based on such a nebulous concept as racial discrimination. A Secret Service Agent should be able to understand and accept such a decision. If he cannot, he has no business being in the Service, particularly given the current nervousness.
The Captain had every right to insist upon the paperwork being correct to every box filled in, all t's crossed and i's dotted. He needed to assure himself that his arcraft, crew and passengers were safe.
It is very, very easy to judge this incident with the 20-20 hindsight of a Tuesday morning armchair quarterback. But he had to decide the case there and then. He did so. Sure, he has later to provide a certain amount of justification, but anyone who errs on the side of safety is OK by me.
Anyone criticising his decision has to convince me that they could be as certain as is reasonably possible that the aircraft was not endangered by this person's continued presence on board. I am (so far) not convinced.