Kos is refering to this:
As a Republican student activist Tancredo spoke in support of the Vietnam War. After graduating from the University of Northern Colorado he became eligible to serve in Vietnam in June 1969. Tancredo has said he went for his physical, telling doctors he had been treated for depression, and eventually got a "1-Y" deferment...
In 1970 after Tancredo's student deferments ran out, he appealed his 1-A draft status, which would have put him at the top of the list for draft eligibility during the Vietnam War. Tancredo was then given a 1-Y status, which put him at the bottom of the list after he reported that he had been treated for mental illness as a teenager.
Markos hurt his widdle feelings, so he took his ball and went home. Boo fucking hoo.