You win more flies with honey than vinegar.
Do you really think picketing in front of someone’s house will make them more likely to adhere to what is tzniusdik or do you think you’ll turn people off yiddishkeit that way?
I think the tznius gemachs (classifieds offering to sew slits, fix necklines, etc.) are more likely to have a positive impact than those who think they have an obligation to shame someone in public.