That's a fairer criticism, although I disagree. You could say "what he actually believes is unknown" about anyone, really. He makes his views quite well known,

That's a fairer criticism, although I disagree. You could say "what he actually believes is unknown" about anyone, really. He makes his views quite well known, at least from what I've followed him. Still, I think replying to someone's quoting Penn with the equivalent of "well he denies climate change, so why would we listen to him?" is pretty pointless for a debate, especially when what you say is wrong! We might as well throw out the ability to quote anyone, since basically everyone has some view that someone disagrees with.