Apparently there is bad behavior all around here, but I mainly blame the family court for attaching such importance to messages like this. It is very common for parents to occasionally chew their kids out like this, and the courts would do nothing if there were no custody dispute. If it is legal for a parent in an intact family to speak harshly to his kids, then why should it be illegal for a divorced dad to do it? By acting on evidence like this, the court just encourages warring couples to escalate their disputes.
This ABC News article discusses how the whole incident may have been provoked by parental alienation and Basinger's history of obstructing visitation, but nevertheless says:
Baldwin has dealt a severe blow to his custody claims in the future. The welfare of children is the primary concern of family law judges. "So regardless of who's wrong and who's right in terms of frustrating visitation rights," says Segal, "if the court finds that you have involved the child to the extent that Baldwin did here, [it] is going to lash out and come down very, very hard on him, regardless if Kim Basinger is the Wicked Witch of the West. This guy has no defense."