Well, there's really no disputing that he got his face demolished.
That's a compound fracture of the mandible and a lot of missing teeth.
As for how it transpired, there are two things there. First, his account for how it went down made him look like the complete douche you make him out to be. He asked the lead gangbanger if he'd have his boys shut up so he could get some sleep. If you're going to make up a story you would probably come up with something that paints you in a less moronic light. Second, the attitude of the guards in that and other privately run prisons is pretty well known to be exactly what he described. It was other Wackenhut guards that testified on his behalf and in fact the State of Texas sued Wackenhut for failing to provide the proper security that they were obligated to under their contract.
And to be clear, I know next to nothing about Prater. At the same time I consider him and his opinions no more or less biased or credible than the opinions of him by a forum of people who by and large think he's the antichrist in a story of five Jesuses.
I'm not arguing that he got jacked up - it's true that he did. And I wouldn't doubt the fact that the guards and Wackenhut didn't do their jobs properly. But I still would question some of the details of his story. Considering how much he thinks of himself (such as his comments about how he fought Derek Oliver to keep JL in the band, that it was "his call" on whether JL stayed in the band or not), I wouldn't be surprised in the slightest if he mouthed off to the gangbangers when making his request that they keep it down - in fact, the records say his response to them when they refused to quiet down was "Well, **** you then, see you in the multipurpose room." which sounds like a completely different person compared to "Could you ask some of these guys, please, because some of us have to sleep." Not that I'm saying that he deserved the beating he got, but I wouldn't be surprised if he mouthed off to some of the wrong people and had to deal with the consequences of that.
As for MP not being any more trustworthy in recalling what went down in Beartracks for the recording of IaW and ACoS, don't forget that there were several others who were quoted in Lifting Shadows that helped tell the story. If it was completely just MP vs. Prater, then you guys might have a point that MP's story is just as skewed as Prater's, but when you see JL arguing that Prater is full of it (see the top of page 102), then I think you need to reassess who's story is closer to the truth.
One further thing - since El Barto brought it up - I realize that Prater had some recovery time after his prison ordeal, but after that was over, what would've prevented him from continuing to produce albums? Especially with the lawsuit draining him financially, I'd expect him to be working double time to try to earn money to fill his drained bank account.