fighting high

I was just on youtube and found this video titled "BJ Penn high?" A related video is of Dana & Chuck at Talladega. So go to youtube and search for the BJ video then search "Dana White Talladega". On the one with Dana & Chuck at Talladega, if you watch a little over to half way in Dana is munching out and says it's from some moonshine. Being from Bama and having been to Dega many a time I suspect he had a little more than a taste of homemade moonshine. Ok aside from the humor in seeing what may be Dana and BJ high, we all know the Diaz brothers smoke. No telling how many other's do. Plenty I'm sure. So my question is, if you are testing fighters for THC...well why? It's certainly not like it's going to enhance their perfromance. Should fighter who test positive be punished?