Without getting caught up in the hard facts of this case, which we may never fully know, it seems there is a general differing opinion of what is acceptable.
Either screaming kids is part and parcel of being a bus driver or it isn't and the driver has the right to ask them to leave the bus regardless of where, when and any other circumstances.
I personally find the latter point of view disgraceful and I'd hate to think that is what is being instructed by the bus companies. For one, parents don't have a choice if their two year old starts screaming and secondly asking them to leave the bus may leave them vulnerable, in danger and quite frankly stuck.
It shows a lack of basic human compassion and I agree, those drivers who don't demonstrate that surely are in the wrong job.