While that is true, what Maher's atheism doesn't provide is any coherent preconditions for condemning anything, including Islam. Although he wouldn't admit it, he's borrowing from the Christian theistic worldview when he condemns "illiberal beliefs that are held by vast numbers of Muslim people." Atheistic philosophy by definition precludes the basis for any such moral claim.
Cordially,
Atheism is little more than peremptory antagonism. It specifies no moral qualities, but ironically requires abstract moral inventions of its adherents — divine designs such as “humanism”.
Perhaps Maher is secretly an agnostic.