if it is unavoidable then it is unavoidable but if it isn't necessary then they shouldn't do it. Pretty easy to understand. Most people traveling with their kids are probably doing it to go on vacation so they are making the choice to do it and should understand that they have an extra responsibility to minimize the way they are affecting the hundreds of other people on the flight. My personal opinion, and the one my wife and I lived by when we had small children, was to not take them on flights until we felt they were old enough to reasonably be expected to behave for the duration of the flight, we inconvenienced ourselves by driving rather than inconvenience everyone else by flying. Fortunately we never had a situation where we absolutely had to fly and I understand that is a reality for some people so I'm not unreasonable about it. But most of it is for recreation and personal convenience and that is what I'm talking bout, that is selfish behavior and should be avoided.
I'm really not sure why that is so unreasonable to some of you, it is really just a matter of courtesy.