For the 90% of the population that are heterosexual, the opposite sex parent is the person who teaches them how to have romantic relationships. There is a reason that little girls love their daddies and that little boys are mama's boys, which has nothing to do with incest or actual sexual behavior. Instead, healthy opposite sex parents allow children to practice flirting and inter-gender behavior in a safe environment, free from sexual pressure. In fact, it is when children are deprived of interactions with their opposite-sex parent that they tend to seek adult attention elsewhere, becoming vulnerable to molesters and other predators. The opposite-sex parent is also important in the life of homosexual children, because they help teach children how to relate to people of different genders. There are recognized behavioral differences between men and women that transcend sexual preference, and it is important for a child to learn to relate to members of both sexes. Finally, having two parents involved in a child's life can be essential to a child's well-being in a different manner. While a parent can involve other important role models in a child's life to help that child learn how to behave as a man or a woman and how to interact with men and women, role models are not a substitute for a parent. Role models, by their very nature, have less authority than a parent, which means that a child cannot turn to a role model for assistance and guidance like they would turn to a parent. The sad reality...

Parents can be unreasonable and they can let events from their pasts color their judgments of their children's actions. Having two parents involved in a child's life makes it less likely that a child's discipline and guidance will be arbitrary. Furthermore, even when a parent has made a decision that is truly in a child's best interest, the reasoning behind such a decision may be beyond a child's capabilities. Instead the child may feel betrayed and unloved. In those instances, it is important that the child have another parent to turn to, rather than feeling as if they need to seek adult approval and support outside of the family.
Given how important having two parents is in the life of a child, it is alarming to see how many parents deprive their children of this right. First, many people enter into divorces rather than doing the emotional work necessary to improve their marriages; this inevitably leads to less involvement by one parent. However, children of divorce can have two parents actively involved in their lives, as long as those parents are willing to work on personal differences and make a commitment to continue to raise their children together. There may be aspects of the other parent that one party cannot stand, but, if that aspect does not present a danger to a child, then a good parent will not allow it to interfere with access to the child. To do otherwise is nothing short of child abuse.