A dedicated fairyist will surely construct elaborate scenarios around the story rather than be forced to admit that a life-long belief is not true. As in my example above.
This is true of all irrational beliefs, really. Giving up a long-held, seemingly solid belief in "the divine" is a hard thing to do. I've only ever met two people who have managed to do it. I certainly don't expect anybody to be persuaded by argument on the internet into doing so. As someone said once (Swift?) "You cannot reason a man out of a position he has not reasoned himself into in the first place." (And woman, ceteris paribus, natch.)
Whether that belief is in gods, ghosts, ghouls, fairies, demons, lizards, Scientology or invisible unicorns, once it takes hold it's hard to let go of it. Especially if it is providing comfort. I speak as a reformed former Christian.
I'm reading David Aaronovitch's book about conspiracy theories at the moment. It's fascinating the lengths people will go to in order to cling on to these ideas, because letting go of them is just too hard. They'll construct ever more convoluted rationales for holding them, and get deeper and deeper into fantasy and fictionalisation. Seems to have a lot in common with religion, myth, magic and superstition.