reason not to have an incarcerated person having a gun: they would likely not stay incarcerated while engaging in further unlawful conduct.
reason for an incarcerated person person being barred from voting: they would likely not stay incarcerated while engaging in further unlawful conduct according to you if it's not a false equivalence.
I think this sufficiently shows the absurdity of your argument. If you want to deprive a person of something be able to make a coherent argument for it to be necessary to do so. Go.