He wouldn't last in the FBI talking that crazy shyt and showing up to co-worker's dinners drunk. He's where he is for a reason.
Fred.
I can actually speak to this. There are hardasses that seem like dumb cops in the FBI. And intellectuals. And there are guys in the FBI who are straight up Jimmy McNulty clones. I know an FBI guy and he seems more like a undercover vice detective with how he acts. Not all FBI agents are straight laced suit and tie type.

his ass. Let's be real here. There is a huge chasm between "not the straight-laced type" and Rust. At some point in the story I fully expect them to mention he's not living up to his potential due to his personality type.