I can excuse Michael J. Fox for the political ad. He's grasping at the illusion that somebody (Republicans) are standing in the way of a possible cure like a drowning man going for a life preserver. The McCaskill campaign, OTOH, is making crass use of a sick individual in an effort to gain a political edge. Michael J. Fox gets a pass from me.
Why should MJF be "excused". No one put a gun to his head making him to make these misleading and lying ads. He did that of his own free will.