Some religious social functions are denied to people who do not believe, or are unwilling to lie to their loved ones about their disbelief. It's one thing to attend church services, quite another to participate in a baptism wherein you swear to the best of your ability to raise the baptized child in a belief you think is a flat lie.

Some religious social functions may be deemed socially harmful, for instance the inculcation of false material or social beliefs in children. (I don't mean false beliefs of the form "Jesus loves you", but of the form "experiencing lust corrupts your mind", "listening to the Beatles will cause you to join a cult", or "yoga is an occult practice and doing it will cause to become insane".)

In many cases, the institution uses its access to members to advocate specific political and social positions which are opposed to humanist values; thus, the atheist humanist may see the organization as a political opponent.