Sounds like no more than a guess. Then again, an impoverished baron would more likely seek to repatriate the taxes originally paid to the king by himself and others instead of preying on his neighbors, now, wouldn't he? Besides, Robin would have joined forces with the other barons (and respected them) to defeat John at the Battle of Runnymede in 1215, because they ALL hated his guts, right? WHY do you think they forced him to sign the Magna Carta upon his defeat, giving birth to the fledgling idea of the rights of men other than the monarch?
If you disagree, take it up with the man himself:
Very little is known about the historical Robin Hood. He did not necessarily even live in the time of King John. The fall of a Baron into poverty could be due to drought or mismanagement. Actually, all knowledge of Robin and his men is guess work based on legends and songs.
In any case, if you can get ahold of Winston's History Of The English Speaking People, (in six volumes, which seems to be out of print), it's a great read!
You can find more information than you probably even want to know about the various legends of Robin Hood HERE
Meanwhile, there is this, from Wikipedia.
References to Robin as Earl of Huntington
Another reference is provided by Thomas Gale, Dean of York
(c. 16351702),[35] but this comes nearly four hundred
years after the events it describes:
[Robin Hood's] death is stated by Ritson to have taken place on the 18th of November, 1247, about the 87th year of his age; but according to the following inscription found among the papers of the Dean of York...the death occurred a month later. In this inscription, which bears evidence of high antiquity, Robin Hood is described as Earl of Huntington - his claim to which title has been as hotly contested as any disputed peerage upon record.
Hear undernead dis laitl stean
Lais Robert Earl of Huntingun
Near arcir der as hie sa geud
An pipl kauld im Robin Heud
Sic utlaws as hi an is men
Vil England nivr si agen.
Obiit 24 Kal Dekembris 1247
This inscription also appears on a grave in the grounds of Kirklees Priory near Kirklees Hall (see below).