I'm on board with Alan on this, with one minor exception. I agree that the agents should NOT delay a train, as others have said, "Get on and ride, while doing your work".
But we as American Citizens, if we DO NOTHING, while this "inspection" is taking place, well it just condones it. You can be sure that the agents will tell you, in no uncertain terms, to "back off or be arrested". Big threat, VERY LITTLE chance of it happening. (I'm not advocating getting in there way at all, just asking them to do their job while train is under way. I would request names of all agents on board, (they HATE that) and then write a letter to supervisors, stating displeasure.
If they get enuff of these letters, they will not be as "eager" to board the trains and delay the trains in the future. If you do nothing, you get nothing..........