In a democracy, all voices are heard - even those of the people who go against society through crime or simply disagree with it. We have to look at, and respect, the opinions of prisoners too and ask ourselves why they do not agree. Voting is rehabilitative because it encourages them to engage with and change a society with which they disagree.
It is easy to feel, in prison, that society has betrayed/failed you because it has brought you to this point in your life. Voting allows you to change society or at least interact with it on a less superficial level.
While, it can be understood, that dangerous, violent criminals may not have the healthiest of ideas, for governing, justly, not all prisoners are violent or dangerous. There are many, who have been convicted, of crimes, simply because they happened to be at the wrong place, at the wrong time. Some of these people, may be totally innocent. There are others, who are actually serving their time, for their wrong doings, which aren't, necessarily violent offences. When their sentence, is completed, they will rejoin society, and again, pay the same taxes, as all other citizens. Since they will be paying these taxes, they should be entitled to voice their opinions, in the same manner, as all other citizens.
No. Prisoners give up their rights when they break the law. This should include the right to take part in the election of public officials. People who are incarcerated have proven their inability to live collectively and effectively with a free population, so why should they have a say in who leads the free population? They need assistance with rehabilitation, but voting should not be part of it.
Prisoners for the most part don't follow the standard rules of all, so why should they be allowed to vote. Voting is a right that must be earned and not rewarded to those who don't follow the law. Most likely if a prisoner were allowed to vote he/she will probably just be concerns in the politics that concern them and not the general public.