Cloning, like nuclear power, is a branch of science that has been unfairly demonized by common Americans more through ignorance than actual merit.
The idea behind researching cloning is NOT to create fully functional clones of human beings. This may be useful for animals or plants, but in people it is hardly desirable. When people think of "therapeutic cloning" for some reason they believe that it means creating human clones as organ banks. This could not be further from the truth. The first key to deciding whether cloning is ethical is understanding what the end goals of cloning are.
The goal of researching cloning is to understand how the human body grows and develops. Despite all of our knowledge, we still do not understand all the different factors that play a part in creating organs or people for that matter. By understanding how humans develop, and learning how to influence and affect that development, we can deal with diseases that create problems with human development, chief among them: cancer. It can also lead to manipulating the human body to the point where maiming and spinal cord injuries are not the end of the world, where such damage can be repaired, if not completely regrown. This never requires the creation of another human being, it simply requires understanding more about human development.
People will claim that there is no such thing as a right to scientific inquiry, and they are regrettably correct. Let us look at it as not a matter of law, but rather a matter of practicality. The quality of life of all Americans has been increased by our continuing expansion of knowledge about biology and the human body. The more we understand, the more we can fix, the more we can keep what was once a death sentence from being any more than a minor inconvenience. Think for a moment about the millions of people who are suffering today from spinal cord injuries, cancer, lost limbs and any number of other conditions that drastically can affect a person's quality of life. Do we not owe it to them to do whatever is required to help them? Is not the purpose of our lives to alleviate the suffering of others?