Many of the states that have these laws against "felons" voting, it is often only while they are serving time or are on probation or parole.
Many people with felony convictions do not know that once they are no longer incarcerated and no long on probation or parole, they can vote just like anyone else.
I will give you that, if you violate the law, you give up most privileges, including the right to vote, but once you have paid your debt to society your privileges should be reinstated, and that should be the case in every state.
Voting Rights are Federal Law, and States are in violation of the Constitution when they make laws that bypass, usurp or overrule the Federal Law. So, most of the laws restricting voting rights of ex-felons are probably unconstitutional anyway.