I'd be interested in what support he has for this claim, both out of idle interest, and with an eye askance to looking at how we can determine whether a figure is historical or not.
Looking at Wikipedia, I find no claims of historicity, the closest we get is
quote:From 1228 onwards the names 'Robinhood', 'Robehod' or 'Hobbehod' occur in the rolls of several English justices. The majority of these references date from the late thirteenth century : between 1261 and 1300 there are at least eight references to 'Rabunhod' in various regions across England, from Berkshire in the south to York in the north.
The term seems to be applied as a form of shorthand to any fugitive or outlaw. Even at this early stage, the name Robin Hood is used as that of an archetypal criminal. This usage continues throughout the medieval period. In a petition presented to Parliament in 1439, the name is again used to describe an itinerant felon. The petition cites one Piers Venables of Aston, Derbyshire, "who having no liflode, ne sufficeante of goodes, gadered and assembled unto him many misdoers, beynge of his clothynge, and, in manere of insurrection, wente into the wodes in that countrie, like as it hadde be Robyn Hude and his meyne." The name is still used to describe sedition and treachery in 1605, when Guy Fawkes and his associates are branded "Robin Hoods" by Robert Cecil.