I don't think anyone has said that, what people have said is that fan protests aren't that effective. If the board only care about getting our money, and it seems they do, then paying money to go and protest is about as effective as the people who bought records in the wake of the John Lennon "bigger than Jesus" kerfuffle to burn them in protest...and then went out and bought replacements. They've still got our money, why would they care about a few banners?
Big, co-ordinated, sustained protest may have more effect but, in practise, that isn't going to happen.
What is childish is insults/abuse aimed at Wenger. It makes the people doing it look like toddlers throwing their toys out of the pram and detracts from their opinions which may well be sensible ones but expressed in such a childish way don't encourage engaging with.