It depends on how you frame your argument. If you end up arguing, in effect, that the guy who's doing a life sentence for shooting a cab driver in cold blood after he robs him is really a political prisoner and the victim of a racist and genocidal justice system then sure -- you're not going to win over any hearts and minds.
But there are plenty of arguments against the U.S. prison system that appeal to mainstream, even conservative sensibilities, like the fact that prison and jail breaks families apart; that it's increasingly difficult for someone with a criminal record to get a good middle class job (e.g. a lot of states won't license plumbers or electricians with felony convictions -- even though they teach these skills in a lot of prisons); that brutalizing someone for years and then expecting him to be a productive member of society upon his release is unrealistic, etc.
In short, I think one can make a compelling argument that incarceration in the U.S., in addition to being unfairly punitive, contributes to the types of social problems that breed the criminal activity that scares hard working, middle class folks.
And if programs that benefit prisoners are so unpopular and fringe, why the hell is Sam Brownback sponsoring the Second Chance Act, a not-bad piece of legislation? http://brownback.senate.gov/pressapp/record.cfm?id=287465
-WD