There is no picture of naked female breasts (breats only) that can be argued to be pornographic.
To call naked female breasts "porn" is to perpetuate female subjugation and body-shaming.
2. As someone who works in abuse, defining porn is really nuanced. You don't get to define porn for yourself, and while I actually do agree with where you stand on cultural norms in general, when it comes to offering public services you actually have to just go with what people find acceptable per country / comply with laws. So in some countries what would be called porn isn't considered that in others (topless women in Europe, or bikini-clad women in USA).
You can argue that all countries shouldn't body shame women or set rules for what they can and cannot wear / especially with double standards vis a vis men. (And I personally hold that view too.) But that's a societal issue / opinion and not related to having to define service behavior, which exists in society and has to comply with its whims.
They reviewed their policies over a year ago and images of breasts are allowed if they're breastfeeding, or after mastectomy (either reconstructed or tattooed or just left) or raising awareness.
http://www.huffingtonpost.co.uk/2015/03/16/breastfeeding-fac...
https://www.facebook.com/help/340974655932193
https://www.facebook.com/help/318612434939348?helpref=search
What you see here are people reporting images, and facebook algos / employees mistakenly banning.