This was rejection, not skepticism, despite what he called it.

Only RMS is in a position to say how much RMS actually considered the points raised.

I'm not as generous as you are in allowing that this just might be an issue of communication. As I understand it, he is a lawyer and also quite clever. I believe that he knew how it would be interpreted when he wrote it.

A rational skepticism is necessary for science to work at all. But radical skepticism is so impoverishing a philosophy that no one, except possibly a few nuts, believes it any longer. And there are several gradations in between.

There is a difference between skepticism and blind rejection. Distinguishing between the two in yourself, I have found, can be difficult because it requires significant and constant introspection.