It is very hard to get a business moral out of Robin Hood. Robbing from the rich to give to the poor is still robbery. Equally drawing parallels with redistributive taxation is a political concept rather than a business one and a minefield that we would prefer to avoid.
Maybe the best message is one of the dangers of putting a natural number two in charge. Prince John was clearly an inadequate substitute for his elder brother and by poor communication and management proceeded to alienate his customer base (peasants, vassals, serfs) such that they refused to grace him with their custom (pay taxes) and resorted to alternative ways of receiving such goods and services (by becoming outlaws).
Historians will probably point out that in reality John was probably underrated as a king and Richard overrated but that just serves to emphasise another important business lesson – manage your legacy.
Done, sorted, next. We’re still not sure about robbing from the rich to give to the poor though….