Yeah, he could have had a vial of Ebola up his ass. Or, he could have had an unseen bomb strapped to his body. Maybe he had an unseen high capacity pistol tucked away in a belly belt holster. The SS should have intercepted him well prior to reaching the front door of the WH. Secondly, I would hope that there was at least one sharp shooter with cross hairs on this asshole as he was galloping across the WH lawn, and that the reason he was not shot is because an order was not given. Of course, there may not have been time to give an order. If so, then what in the world is the protocol to be followed in this situation?
In hindsight, the SS made the correct call. However, they just got lucky. Next time it may costs lives.