Wow. His entire argument against the statement disappears if he cannot show it is incorrect. Yet all he does is show that the external world might be some sort of consciousness or might be physical.
Could you explain what you mean by 'physical'? I doubt realism, but I don't doubt the external world is physical. Do you mean tactile?
Don't forget that dreams are physical. There's no difference between a dream and waking reality in that respect. A very eye-opening experience for me was when I examined the "qualities of matter" during a lucid dream. They are identical. That experience should give anyone pause, to say the least.