I think a big part of the backlash is a reaction to how many media members loudly declared Josh MVP during the stretch against KC, San Fran, LA and Detroit. Lamar's numbers were good enough that it was interpreted as disrespectful, especially considering how sensitive Lamar backers have been over the course of his career (in some cases, for good reason).
It also smacks somewhat of entitlement, though. Praise of one player isn't intended as disrespect toward another and Lamar sure as hell isnt the greatest QB to ever play the game as Harbaugh said last week.
This MVP result is going to leave a stink in its wake regardless of who wins. The NFL has reached a media saturation point where there are simply too many voices mouthing off baiting for clicks and views.