I agree that people in prison should be doing some kind of work. But it shouldn't be harsh in the way that "labor camp" would imply, and there should be some element of choice about the type of work. Some type of restitution from the offender is important.
I certainly agree with the bolded part, but I'm not sure how protecting rapists and murderers from "harsh" labor accomplishes this. Let me emphasize the point that I am not suggesting we convert the entire prison/jail system into a system of "labor camps"; this would be a punishment for offenders of the highest degrees (rape, murder, terrorism, etc). There could be a less rigid community service program for lower level offenders.
People who commit the worst crimes still ought to be treated with some basic level of respect as human beings. Otherwise you end up with Abu Ghraib.