Some religious social functions are denied to people who do not believe, or are unwilling to lie to their loved ones about their disbelief.
The exact same thing could be said about secular-humanist organisations - suggesting that there's nothing inherently wrong about such a standard even from your perspective. Sure, they outwardly profess being much more open and accepting than institutions of traditional organised religion, but the overwhelming majority probably wouldn't accept a creationist baptist or a wahhabi, for good reason - and the same goes for religious institutions. I don't think anyone should be forced to associate with people who openly reject and oppose their world-view, which seems to be what you're proposing.
This thread is for asking any questions that might seem obvious, tangential, silly or what-have-you. Don't be shy, everyone has holes in their knowledge, though the fewer and the smaller we can make them, the better.
Please be respectful of other people's admitting ignorance and don't mock them for it, as they're doing a noble thing.
To any future monthly posters of SQ threads, please remember to add the "stupid_questions" tag.