We live in a world where people are MORE outraged about the photo being taken than the utter total lack of respect for the other diners who really didn't expect to pay for their meal with an added side of a mid-meal poo for entertainment. That says a lot really.
The world does not stop rotating because you have a child, other people's rights to a decent, hygenic, intrusion-free meal don't vanish because you have a child, the restaurant's rights to not have environmental health all over their ass and their custom leave because of this don't vanish because you have a child.
I imagine whoever took the photo was so shocked at what was going on and felt, like lots of people do, that you're right-less up against someone with a child who'll just go ballistic on you if you point out that "hang on - that's really not on" that they did the only thing they felt they could do to convey how utterly disgusting the behaviour was - hopefully the public reaction gets the message across for anyone else wanting a bit of between course potty training as well.