Should Denying The Right To Vote Be Used As Punishment ?

This is something that has bothered me for quite a while. Most of the states in this country (all but a couple) take away a persons right to vote if they have been convicted of a crime. Some return that right after a person gets out of prison or completes parole, and others do not.

When a person is convicted of a felony and imprisoned, those same states cannot deny other rights (according to the Supreme Court) -- such as having decent food and shelter and medical care. How then can we justify denying the right to vote? Isn't that one of the most important rights of any American -- a right that is basic to the preservation of our democracy? Personally
The American Civil Liberties Union (ACLU) says:

A patchwork of state felony disfranchisement laws, varying in severity from state to state, prevent approximately 5.85 million Americans with felony (and in several states misdemeanor) convictions from voting. Confusion about and misapplication of these laws de facto disenfranchise countless other Americans.

Personally, I think this is wrong. The incarceration of an individual (or probation/parole) is the punishment for the crime he/she committed. There is no rational reason to compound that punishment by also denying a basic American right -- the right to vote. The right to vote should never be denied to any American citizen for any reason.