Well, there seems to be enough evidence about immune benefits from breastfeeding, that if someone doesn't want to bf for cosmetic or light convenience reasons, say, then some social opprobrium may be appropriate. There's a whole gradient of "is it society's business" from "what do you name the kid" to "do you seek medical care when the child is sick" to "do you even feed and clean the child".

And of course, in the recent past corporate society made it its business to push formula as a mark of Progress! and Science! where it wasn't needed, and a lot of people are still reacting to that, I think.

Of course, if all one knows is that X is using formula, one doesn't know if that's because X couldn't bf adequately, or X would lose her job by doing so, or because X thought it'd be too messy and troublesome, so people shouldn't go judging X.