However, letting your child wear a costume that's been in the family for generations is not bigotry alone. If she went out with him trick-or-treating while shouting "kill all niggers" or "God is white", that'd definitely be bigotry.
I believe that bigotry is active. I don't believe that bigotry is passive. Do you believe anyone who burns the American flag should go to jail? We're on the same premise here if you do.