The driver's first responsibilty is to the safety of the passengers on his bus, and indirectly to the safety of other motorists on the road with him.
It is a judgement call as to whether any given individual on the bus is creating a distraction that is impairing the driver's ability to cope with that primary responsibility, and if the driver is not allowed to make that judgement call, safety will suffer as a result.
Therefore any individual who distracts the driver from Task #1 is subject to being removed from the bus.
If I were the driver, would I have put her off? Probably not. I'm arguably a bit more used to crying children as a single parent. I might have asked her to move to the rear of the bus if it was loud enough to be distracting.
I wasn't there, I wasn't the driver, and the driver is the one making that call as to what interferes with his ability to perform Task #1.
Riding the bus isn't a right, to my knowlege. It is a convenience provided for city dwellers and provided by gov't or private contractors, either to make a profit or to keep auto traffic down or as PR bait, or all the above. I don't know that anyone has a right to ride the bus if they're making it hard for the driver to fulfill his number-one responsibility.
Now, the driver's employer has decided that he acted inappropriately... or at least that is what they're saying for public consumption. They gave her some free tickets and said "sorry" and said the driver would be monitored more closely in future. Ok then. What do you want, the guy's head on a pike?
Frankly I just don't see this as that big of a deal really. If the Mommy in question wasn't a reporter herself this probably would not have made the news.
If it had happened to me, I'd be annoyed, yeah. But if you don't want to risk being removed from the bus for having a crying child, get a car and drive I suppose.
I guess you could mark me down as "Meh."