Clearly some are more at risk though.
If you throw some manger in with the sharks knowing full well there is greater chance he'll be shredded than your average robber would then I don't see how the jailers can abdicate responsibility on the basis of 'this is prison, shit happens'
It doesn't fit with western ideals about justice.
Every prisoner has (and would have) the same protection. Prison guards do what they can to keep weapons out of prisoner's hands for the protection of themselves and any other inmate. They do what they can to prevent fights because fights can lead to riots which endanger themselves as well as other inmates.
Again, what should happen to them was my words. What would be happening though is we just wouldn't be giving people extra protection based on their crimes.
You have a constitutional right to due process and against cruel and unusual punishment. You have no constitutional right to extra protection based on the type of crime you've committed.