No, I do not think parents should be required to take parenting classes before being able to parent. After all, parenting is a natural thing that comes as mother, father, and child(ren) begin learning and growing together. At birth, there is a natural bonding process that begins and for the mother, it begins at pregnancy.
There is no text book way to parent and no book that will ever truly tell you how to raise your child. Every person is different and will, therefore, raise their child different.
On the other hand, there are parents out there who have taken the wrong paths whether it's general irresponsibiity, drugs, theft...and the list goes on. Some have had their children taken away and some that haven't. I believe these parents should have to take parenting classes before being able to get their children back. It isn't fair for the children of our society to suffer because their parents are unresponsible. What most children that are in these types of homes don't know, is that their parent does love them but they are just aren't good parents.