If he actually wants to help users, he can let users click through via Apple login on his site, then ask those users to also authenticate via one of the other methods (e-mail, Google or Facebook) and link the two. That way, he would be able to let his users still log in to their accounts via e-mail if Apple tries to shut him down (like Google did temporarily).
I think his focus should be on limiting potential damage to his users, not exacting revenge against large companies.