Being an ex-con should not disqualify you from driving a cab. Especially in a country like the US that has obscene incarceration rates, and where who ends up in prison is a factor of race and wealth more than the seriousness of the crime.
An ex-con has paid his or her "debt to society" by being in prison. If we don't let them get a job and earn a living, how will they get rehabilitated in society?
Edit: typo/car/cab.