"what difference does it make whether or not he is "defrocked"?"

It'd would show that the institution takes the matter seriously and totally condemns a person for what is a grievous crime against innocents. The priest for life thing is a surely a red herring? You admit yourself that priests are defrocked for other non-criminal reasons. I think many people would find the idea that holding a different opinion over some doctrine warrants defrocking whilst abusing children within your care doesn't quite bizarre!