This is ridiculous. A new grad student shows up and refers to his new colleagues -- not once, but twice -- as "bitches"? Obviously, this student has some payback coming his way, which I applaud. But keep in mind that this student got into the program in the first place. I'm guessing his undergrad GPA and/or test scores were respectable enough, but why didn't this sort of behavior get reported in the letters of recommendation? I can't believe this was the first time he'd behaved this way.
I rarely if ever trash a student in a letter of rec. If I don't feel that I can in good conscience give a nice letter, I'll decline to write one rather than say bad things. But what happened here? Did people write letters ignoring this student's behavioral problems? Or did the student just find the two or three people who didn't know him at all but were still willing to write letters? Either way, it's a problem.