He was carrying $4700 in proceeds from book t-shirt and merchandise sales from a libertarian political rally in St. Louis. His fear was that Missouri had published guidelines that included Ron Paul supporters as profiled domestic terrorists. The TSA dudes had also seen and read political literature he had in his posession and knew his political affiliation. The harassment stopped when an FBI agent stepped in and whispered to the TSA agents to let him go. They did.
Note to self: Always carry an FBI agent with you when traveling.
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.