It's not an unfair advantage if it's by the letter of the rule. It didn't change the game, but it may have altered the outcome. Calvin Johnson can't fumble that ball, end of story.
It is an illegal bat if:
a) any player bats or punches a loose ball in the field of play toward his opponent's goal line
b) any player bats or punches a loose ball (that has touched the ground) in any direction, if it is in either end zone
c) an offensive player bats a backward pass in flight toward his opponent's goal line
Exception: A forward pass in flight may be tipped, batted, or deflected in any direction by any eligible player at any time.
Note: If a forward pass that is controlled by a player prior to completing the catch is thrown forward, it is an illegal bat. If it is caught by a teammate or intercepted by an opponent, the ball remains alive. If it is not caught, the ball is dead when it hits the ground.
Wright illegally batted the ball, the Lions should have been given the ball at the 1-yd line with goal-to-go. You cannot arbitrarily say it's an unfair advantage when the advantage is given to the team by the rule. It the same advantage given to players with simultaneous possession, defensive PI, intentional grounding, etc. Punters kick the ball out the back of the end-zone and it results in a safety and forfeiture of possession, so the rules are not the same.