Could you (or anyone else) possibly provide me with a clue as to how I might find E.Y.'s opinions on this subject or on what you base that he's an infinite set atheist.

Well, "site:lesswrong.com 'infinite set atheist'" is a clue, but http://lesswrong.com/lw/mp/0_and_1_are_not_probabilities/hkd is also a place to start.