When convicted of a crime, prisoners should lose all rights except the basic rights of food, clothing, and shelter. Prisoners have shown that they make poor choices or else they would not be in prison in the first place. Voting rights should be giving only to those that have not been found guilty by a jury of their peers. I am not saying that once they are released from prison they can't vote, but that is a debate for another occasion.
Prisoners are still citizens and should be allowed to vote. Some issues directly effect them more than others and they would provide a valuable insight into prison systems and corrections. Allowing them to vote encourages civil responsibility and fosters a sense of purpose and value that may prevent them from committing future offenses. The right to vote is just that - a right.
When taking away a right it is just like slavery all over again, yes they have made bad choices but they are no less of a person than you nor I.
And if you disagree then a compromise could be made where it is only a certain type of prisoner like a minor offence such as petty theft.
By not allowing prisoners to vote, we are allowing the same discrimination that African Americans and women were forced to bear before they were granted these rights, a problem that I had thought we had moved on from long ago. Continuing to deny them these rights that every American citizen should have, we are denying these people a voice, which according to the Constitution everyone (no matter who they are) has a right to have.