To care about something that isn't a person to the degree that one cares about persons is wrong. It is a distortion of love to care in that way for a non-person, and it is a kind of disrespect to those who are persons when one cares for other things as much as persons deserve to cared about. (One thinks here of the implicit insult to children when someone loves a pet the way one loves a child.) But it is not wrong to care in this way about severely developmentally disabled humans. Hence these humans are persons.