So as to why the cops would call a k9 unit over a simple traffic stop in Tennessee, it's pretty simple. A few years ago, and probably still, Tennessee had the most active court system in the nation simply due to the sheer amount of drug crimes being prosecuted. The area is a major location for manufacturing and transportation of meth. So no shit the cops will be calling a k9 to a traffic stop when they see a clear lunatic.
This is of course, assuming any of his details of the arrest are accurate. His time spent in jail story seems to be full of bullshit and doesn't really match with any procedures I've seen or heard of, although my experience there is a bit limited.
TL

R...don't look like a fucking fiend when you get pulled over in a state with a massive drug problem.