I agree with Christina.
The reason that many [Photographers] dislike it when they see selective coloring, is because it's so very often done poorly. Not necessarily the technical aspects of of doing it, but the choice of what to color/not color is a poor choice.
It's pretty obvious that leaving a small part of a photo in color, while desaturating the rest of the image, will cause the viewer's eye to be drawn to the part that is in color. It will likely cause that part to be the strongest focal point in the image. But should it be?
The example I see quite a bit, is when there is a shot of a baby with a bow or flower on their head. The shot is converted to B&W but the flower or bow is left if color. So what are they trying to say with that photo? That the bow is more important than the child? That's probably not the case, unless they are trying to sell bows.
The focal point of a portrait should be the person/people in the photo. And you usually want to draw the viewer's attention to the face & eyes the person. If you draw their attention away from the face, it usually becomes a less effective portrait.
Plus, I just think there is something morbid about leaving something in color along side a colorless baby.