If Mazursky was such a badass then he would've ....
First, I thought Ben Foster did a great job playing the psycho older brother Jake Mazursky. Every scene he was in was a stealer. And apparently he had a good opportunity to play the character as the real-life dude actually was...
But if Mazursky was such a badass, he would've taken this all out on the San Diego connection who ripped him off selling the "bunk" E-tabs. This was what the original drug debt was all about. Mazursky was supposed to collect for Truelove from a dealer in SD, and instead of collecting the money he accepted bunk drugs as payment and would up getting ripped off. And he didnt go back down to SD and crack the dude's head - he went to Truelove with a story about how "we" got ripped off....which put the fateful events in motion.
Mazursky was either a dumbass or not as tough as he was depicted in the movie, most likely both. A real badass to be feared, he wasn't.