Reading further, it seems like the underlying issue is the airline not wanting to make bassinet space in first class. So, I'm guessing the age of a baby will be under one year.
I admit that I can understand how it would be upsetting, maybe even infuriating to pay for first class on a long flight and not be able to sleep.
Its not toally logical though because a 2-3 year old might be more obnoxious than an infant. When we flew home from Korea with our new 5 year old son, he was probably very difficult for many passengers. (He was certainly difficult for us

). We didn't fly first class, but I'm sure that there would have been some disappointed passengers if we had

. What I'm saying is that if they are truly worried about their first class customers comfort, then they would probably ban all children under some older age than infant. It seems that the real issue is how many first class seats they can fit on their new planes. Regardless, this will make many people happy - and I do understand that.
I just don't like some of the general attitudes in society about babies and children - that's what made me uncomfortable with this.