The union claims, among other things, that "poor pay" leads to corruption. That's right, people aren't responsible for their own corruption, they can blame their salary.
If prison employees aren't getting paid enough, maybe they should go look for a different job.
Libertarians know what this all comes back to: the war on drugs. Without that, we'd have a lot fewer prisons, prisoners, and prison employees, lower taxes, and a lot less corruption to worry about.