Well, you know the rest. More evidence here.
The larger point here is that everyone knows Michael J. Fox has Parkinson's. That's not debatable. It's not capable of being spun or attacked for political gain. Parkinson's and other diseases could very well be helped by stem cell research. If Republicans are going to oppose such science, then they better be prepared to see the results of ignoring the science. Fox is asking for help and he has every right to do so in the course of the election discourse.
Limbaugh, by contrast, so callously demonstrates why people have had enough of Republicans. They'll say anything, do anything to win. Even publicly trash a man with Parkinson's.