He probably shipped all that merchandise ahead of time. I doubt he could have carried it all on the plane. Either that, or he was selling dope, or he just wanted to carry some cash and make a scene.
The TSA dudes had also seen and read political literature he had in his posession and knew his political affiliation.
That's probable cause for suspicion of selling dope right there.
The stuff was sold out at the rally. There was nothing to ship and there was no reason to suspect drugs at any point.
The TSA employees over-reached and the traveler was not ready to give out information to a bunch of baboons.