yes they should.
If jail is to both punish and encourage people to learn the error of their ways then treating them without any human decency means they will more likely offend when they come out.
BUT! I know there are scum in there who deserve no respect etc for their heinous crimes, yet I believe they are citizens of the country and should be able to vote.
Colour tellies in the rooms, no. Vote, yes.
(and please don't call me a washy liberal and provide examples of terrible criminals, I know the stuff.)