I personally don't think Toni Morrison makes a specific judgment on what Sethe does. She leaves the interpretation up to the other characters in the book as well as the reader. Paul D. and the rest of the community end up demonizing her because of what she did.
The community seems to understand why Sethe killed her daughter, but they cannot grasp that she actually did it. When Sethe came back from jail, she closed herself off from the community (maybe out of shame) and this is why the community ends up turning their backs on her. They saw her withdrawal as an act of pride.
Paul D. at first has trouble believing that the woman in the newspaper Stamp Paid shows him is really Sethe. He keeps saying it can't be her because that's "not her mouth". I think that this is, in part, his way of still trying to see her the way he saw her at Sweet Home. Back then, he mostly saw her as a woman to desire; and while when he shows up at 124 all these years later and still does see her in this way, he also sees her as more. Paul D. is suddenly faced with having to see her as someone who is capable of murder.
Sethe is constantly trying to explain why she did what she did. She tries to justify it to others, but, it mostly seems like she is trying to justify it to herself. She seems conflicted. She talks like she believes she did the right thing, yet when Beloved starts to guilt-trip her, Sethe becomes consumed with regret. She ends up apologizing numerously to Beloved for "leaving her behind".
As far as my judgment of Sethe, I think it's kind of hard to say it was either right or wrong. It's not a black and white situation. I am deeply sympathetic towards what many enslaved women like Sethe had to go through and I know all about the issue of infanticide. I can understand why Sethe thought it was necessary. She really only wanted to protect her children from living their lives in the same, awful way she did.
