Heat. That's what you usually have to do to get red loctite off. I think I remember reading something else that dissolves it, but I can't remember what it was. Maybe try to Seafoam Deep Creep or something like that and let it soak in and see if that helps.
This is why I never ever let anyone else mount a scope for me anymore. I've never had a good experience letting a shop mount a scope. Too many idiots out there. You should never ever use red loctite on anything scope base, or ring related. Use the blue if you are going to use it.