The relevant distinction is not "punching up vs. punching down", which is meaningless, but "punching at actual misuse of power or not". It's very rare that shaming is a useful tool, but it can work indirectly as a form of raising awareness where the "shame" is really just a ploy for virality. Harvey Weinstein, mentioned in the article, is a perfect example: he was engaging in behavior that was not only grossly unethical, but raised very real questions about actual legality. That's where "shame" can work for good.