People going through a divorce may be willing to do things they would usually find immoral or inappropriate. Even someone who has always had an egalitarian approach toward parenting may change when it is their family going through a divorce. Someone you thought you loved and knew can change into a total stranger through the course of a divorce.
The desire of your ex to hurt you or feel vindicated could lead to all kinds of inappropriate behaviors. They might even go so far as to deny you visitation or parenting time with your children. Sometimes, people are overt and obvious. When you refuse to accept their requests or meet their demands, they immediately inform you of their intent to withhold access to the children.