::::  What person with more than a 3rd grade education is not going to understand the term 'treason'? In any case we can say that Arnold became a traitor against the American cause, as again, Arnold is synonymous with traitor and virtually all sources refer to him as such, whether outright or definitively.  There's a not so fine line between 'rebellion' and 'treason'. Washington, Jefferson, et al, voiced their complaints for years against an unyielding British crown which finally culminated in wide spread rebellion and revolt. This is tot the same as treason, where you pretend to be loyal to a cause, and then turn traitor. I could be mistaken, but I would think not even British historians have ever referred to Washington as a traitor.