Without removing all non evil factions and adding an evil one, is there a way for a script to make any crimes against a specific NPC ok? Basically I need them to be effectively evil, so people don't care what is done to them, but without altering the base object.

As long as an NPC is part of one or more evil factions and not part of any non-evil factions, no one will care what's done to them. You could tear out their ribcage and wear it as a hat, remove their skin and use it as a tapestry, dangle them from a rope and set them on fire, steal from them, hit them with a weapon or otherwise abuse them and no one will think less of you. They might even join in.

You can use a script for setting factions without altering the base object. You can use SetFactionRank to remove any non-evil factions the NPC is part of. That part of the script would look like:

ActorRefID.SetFactionRank FactionID -1

This will remove the desired faction from the NPC.

Thanks, but what I need is a way to make an actor effectively evil without altering their factions. Is there any way that a spell, piece of clothing (something like the gray fox's hood), or maybe an activator could render any actor evil without changing others of the same base object? I do not have OBSE, but I'm sure I could get it if it is necessary to do this. Maybe some script so that every time the player assaults or kills them, if they are seen, it mods their bounty and crime record to remove the offense. I don't care about theft laws, only attacks. If anyone would know how to do that, please tell me.

NPCs will only be considered 'Evil' if they belong to at least one evil faction and no good factions. The only way (that I've ever heard of) to make them evil is to remove all non-evil factions (if any) and add an evil faction (if necessary).