So we should just use shame appropriately.
But that's all besides the point. Judging by myself only of course, I seriously doubt people shame others because of the duty to higher purpose (making people civilized).
That makes sense to me - do something dumb socially, the repercussions should be social as well.
Shaming has rather drastic negative consequences, especially in communities that shame intelligence, education, gender, race, neurotype, etc.
It's a non-violent tool to shape societal or group norms. If you are in a shitty group (e.g. one that shames education), that doesn't change the argument.
“You we’re texting and driving. You could have killed someone!”
And if you genuinely believe people posting selfies are narcissists, does this mean you should ignore and keep quiet?
The latter does not seem to clear cut; there are likely better, more positive ways to change behavior. Shame is more likely to make the person get better at hiding their irresponsible behavior, which is actually counterproductive for society.
I'm still not convinced that shame is ever a useful tool.