Who made the rule about speaking no ill of the dead? Today a long time local radio personality died and the local news interviewed people that knew and worked with him. It didn't take much reading between the lines to know they pretty much thought he was an asshole.
it's not a rule. it's a custom. it was probably once thought to be bad luck; now it's thought simply to be inconsiderate. someone who has just died probably has loved ones who are in some kind of pain, grieving for their loss. it would be inconsiderate to burden them with insults.
g