SaturnV - as you correctly say, the problem with the flight cancellation was American's.
As I have said several times now, I really cannot understand why this captain (or whoever was given the task of verifying the agent's ID) would have not done the two things that would have confirmed it in minutes - checked with the gate agent re the cancellation of the original flight (and hence the glitch in paperwork); and had AA Security call the USSS ... especially as the flight had been delayed by over an hour!!
At the very least, this is poor judgement on that individual's part; and at most racism from the point of view that he's not having any gun-toting Arabs on his flight (regardless of their nationality and employer).
If the latter is the case, what will happen if an Arab-American skymarshall is assigned? Will that person similarly be denied travel?
Again, as I have said before, Federal agents are required to carry their personal weapons at all times. No ifs, buts or maybes. Failure to do so results, I am told, in pretty drastic action. These are not hick cops from some one horse town - these people have generally gone through at least as rigorous recruitment, selection and training processes as the average airline pilot - and with them, they genuinely do both put their lives on the line and make life-changing decisions for other people on a daily basis.