As someone who is occasionally accused of misquoting and misconstruing Peter Singer vis a vis his views on infanticide for disability, I would like to call attention to his own explanation on his Princeton web site:
He says it is all right to kill disabled babies. Perfectly fine and ought to be allowed.
But even though he has carefully argued that newborn babies in general are not "persons" (and you should read his own explanation of what a "person" is, so I am not accused of misquoting), he notes that it is really and actually only OK to kill disabled newborns. I mean, after all, they are disabled.
Princeton pays this man an awful lot of money to teach these principles. He has an endowed chair, which means he is never going to be fired no matter what he says. It is apparently OK to preach that a certain segment of the population ought to be killed if no one wants them. This is not "hate speech" at all, because a logical argument has been made.
If it is logical, it is true and therefore valid.
Is there such a thing, really, as a living human non-person? Is there any reason we cannot extend Singer's argument that a"person" is "a being who is capable of anticipating the future, of having wants and desires for the future"? If, say, a living human can't prove he or she ever had wants or desires for the future but has exceeded the magic 28 days of human life, can't we just kill them at that age, too?