"Drug Store Truck Drivin' Man" is a song, originally by folk rock band The Byrds, and released on their 1969 album "Dr. Byrds and Mr. Hyde". It is probably more famous for the cover version sung by Joan Baez at Woodstock, with slightly changed lyrics.
The song was written by Roger McGuinn and Gram Parsons as part of a feud with Ralph Emery, a Nashville country radio DJ that had disparaged their attempts to sing country songs. The lyrics revolve around the squareness of Emery, summarized in the statement that "He sure thinks different from the records he plays". One of the statements in the song is spurious and doesn't seem to be based on anything factual, when they claim that he is "The head of the Ku Klux Klan." Despite conservative tastes in country music, I can't find any evidence that Emery supported the KKK.
At Woodstock, Joan Baez sang a version of the song dedicated to then-California governor Ronald Raygun (ZAP!), with slightly altered lyrics.
Although the exact reason for the song might be lost, and some of the lyrics also might not make much sense (why, exactly, will he be lucky to get out of town?), the song to me does spotlight a certain personality type I have come across many times. In the "country" world, and indeed in a certain subset of American society, you will meet people who are proud to be rule-breakers, rabble rousers and rough-hewn rebels--- but also will get angry at people, often young people, who don't follow traditions. There are people who might be getting in bar brawls one weekend and attending the sheriff's barbecue the next. And these people are who this song is about.