Because he’s either innocent until proven guilty or he’s served his time.
presumed innocent until proven guilty… Is a procedural doctrine for courts. It doesn’t change the reality of whether or not the individual committed a crime.
You murder someone, you’re a murderer, regardless of if you have really good attourneys or you’re really good at hiding the body, etc. the presumption of innocence it to protect the rights of accused people; but has no bearing on actual guilt- even if the court of law finds them not guilty.
while the guy presumably has served his time and deserves fair treatment… the OP is also justified in raising this concern with management. Not that management will do anything, because they’ve already determined it’s not a problem. They will, perhaps, accommodate the OP in scheduling them on opposite shifts or placing them away from him.