People who have served their time, either probation, jail, or prison should be restored to a normal status of citizenship. They should be able to get licences to work at trades and professions and not be discriminated against.
If they have served their time and are back in society, let them have a real chance to get back into society (or else why let them out at all)?
Someone with a criminal record can typically not get a licence to be a nurse, a/c repairman, or even a real estate sales salesperson. In fact, it is nearly impossible for them to get a job at a grocery store or fast food restaurant.
Considering they have successfully served their time and been punished or rehabilitated, doesn't it make sense that they should be protected by law like everyone else against discrimination?