Actually this is a legit issue. What's stopping a bunch of prisoners voting for a candidate(DA) who promises more lenient sentences or looser laws on say sexual assault? It's such a can of worms especially considering a lot of prisons are in rural areas and prisoners often outnumber the people that actually live there.
If your best justification for disenfranchising the incarcerated is that they might selfishly support bad policies, you're going to freak out when you find out how everyone else votes.
Voting is a way for people to participate in society and again one of the point of prison is to lock them away from normal society so they should not have the right to vote in prison. In prison many of your rights are taken away and voting should definitely be one of them
You know, one long-established and pretty stable democracy that does give prisoners the absolute right to vote (and in which prisoners do vote and in which the votes of prisoners have often mattered) is actually Israel.
Well the American system works far better than Israel's does and I would say its still the best in the world or at least in the top 3.
