My uncle posted a picture of Obi-Wan to Facebook thinking it was Jesus. Am I an a-hole if I let him know, or am I an a-hole if I don't let him know? Either way I won't call him out publicly. But you should know that he avoids me because I no longer share his faith.
Stay out of,it. Not your circus, not your monkeys.
I always correct people who make BIG mistakes. If I like the person I do it in private.
That one shows up frequently on my feed. Mainly with a comment of people being afraid to share for some odd reason. I responded by asking, "Why would anyone one hesitate to post a photo of Ewan McGregor?" I was ignored.
That's the exact one that my uncle posted.
There is no action, A, that you can take in any situation, S, were some person, P, cannot consider you an asshole.
You are under no obligation to spare your uncle the shame of his own ignorance; although your compassion for him is commendable, he will probably just see it as trying to get one over on him by correcting him.