Perhaps somebody could put a sign in their garage about the HOA in big bright letters. Something many wouldn’t say in polite company.
That would not bring as fast and as effective results as a large sign in the garage saying, "Jesus Christ came into the word to save sinners (including HOA members)."
The HOA could also be charged with being sexist and insensitive, since men are responsible for the majority of garages, and would be most offended by leaving them open.