By definition, everything they do is natural.
Why would the genetic alteration or enhancement of one more species - homo sapiens - be China FDY dope dyed Manufacturers of any consequence? In what way are humans "more important" to nature, or "more crucial" to its proper functioning? In our short history on this planet, we have genetically modified and enhanced wheat and rice, dogs and cows, tulips and orchids, oranges and potatoes. Why would interfering with the genetic legacy of the human species be any different?
Effects on Society
Cloning - like the Internet, the television, the car, electricity, the telegraph, and the wheel before it - is bound to have great social consequences. It may foster "embryo industries". It may lead to the exploitation of women - either willingly ("egg prostitution") or unwillingly ("womb slavery"). Charles Krauthammer, a columnist and psychiatrist, quoted in "The Economist", says:
"(Cloning) means the routinisation, the commercialisation, the commodification of the human embryo."
Exploiting anyone unwillingly is a crime, whether it involves cloning or white slavery. But why would egg donations and surrogate motherhood be considered problems? If we accept that life begins at the moment of fertilization and that a woman owns her body and everything within it - why should she not be allowed to sell her eggs or to host another's baby and how would these voluntary acts be morally repugnant? In any case, human eggs are already being bought and sold and the supply far exceeds the demand.
Moreover, full-fledged humans are routinely "routinised, commercialized, and commodified" by governments, corporations, religions, and other social institutions. Consider war, for instance - or commercial advertising. How is the "routinisation, commercialization, and commodification" of embryos more reprehensible that the "routinisation, commercialization, and commodification" of fully formed human beings?
Curing and Saving Life
Cell therapy based on stem cells often leads to tissue rejection and necessitates costly and potentially dangerous immunosuppressive therapy. But when the stem cells are harvested from the patient himself and cloned, these problems are averted. Therapeutic cloning has vast untapped - though at this stage still remote - potential to improve the lives of hundreds of millions.
As far as "designer babies" go, pre-natal cloning and genetic engineering can be used to prevent disease or cure it, to suppress unwanted traits, and to enhance desired ones. It is the moral right of a parent to make sure that his progeny suffers less, enjoys life more, and attains the maximal level of welfare throughout his or her life.
That such technologies can be abused by over-zealous, or mentally unhealthy parents in collaboration with avaricious or unscrupulous doctors - should not prevent the vast majority of stable, caring, and sane parents from gaining access to them.
Appendix - Arguments from the Right to Life
I. Right to Life Arguments
According to cloning's detractors, the nucleus removed from the egg could otherwise have developed into a human being. Thus, removing the nucleus amounts to murder.
It is a fundamental principle of most moral theories that all human beings have a right to life. The existence of a right implies obligations or duties of third parties towards the right-holder. One has a right AGAINST other people. The fact that one possesses a certain right - prescribes to others certain obligatory behaviours and proscribes certain acts or omissions. This Janus-like nature of rights and duties as two sides of the same ethical coin - creates great confusion. People often and easily confuse rights and their attendant duties or obligations with the morally decent, or even with the morally permissible. What one MUST do as a result of another's right - should never be confused with one SHOULD or OUGHT to do morally (in the absence of a right).