The author fails to mention one significant factor to the self-segregation of prison populations in the federal prison system. The federal hate crime law makes an assault upon a person of a different color punishable by a mandatory 25 year sentence.
So, if a white had a problem with a hispanic, he had to take it to the white shot-callers (gang bosses) who then went to the hispanic shot-callers. The hispanic bosses would then discipline their member (which could entail forcing him to repay a debt, or assaulting or even murdering him). As long as the violence didn't cross racial bounds, the hate crime doesn't apply.
So, if a white had a problem with a hispanic, he had to take it to the white shot-callers (gang bosses) who then went to the hispanic shot-callers. The hispanic bosses would then discipline their member (which could entail forcing him to repay a debt, or assaulting or even murdering him). As long as the violence didn't cross racial bounds, the hate crime doesn't apply.