There was clearly no targeting. Redfield hit him in the shoulder pads with his forearms. The hit was from the side, not the back. But, blindside hit? Maybe, due to the viciousness of the hit.
The call was roughing the passer. What the official did not acknowledge was that Gardner was no longer a passer as he had made a move towards the ball carrier. He was now attempting to get in a position to try to tackle Shumate. The fact that the hit was so viscious could have warranted an unnecessary roughness call. That would have been the same rule then as now. But the call that was made was wrong.