Correct, Mengzi will agree with this. He's saying that we have the capacity for goodness, and not that we are born to do good. He'd also agree with your point on Singer and Pinker. Depending on some commentators, Mengzi does argue that cultivation through education and socialisation is important for us to develop these moral emotions. Without apt development, we won't go anywhere.

I was once asked about the origins of the universe. So, here I am doing philosophy. Ethics | Intellectual History | Chinese Comparative Philosophy