I don;t think you need to go as far as to say it should be a FREE KICK for raising the arm, but it should definitely not be a free against the tackler. Making it a free for raising the arm would punish those generally trying to shrug a tackle. That's all it has to be, play on if you lift the arm and draw the contact. Maybe it could be considered prior opportunity, but the prior rule doesn't even really exist any more so it's basically a moot point though.