C-sections are not unethical at all, although the question of their medical effects can't be commented on here. C-sections are as natural as any other medical procedures, and can prevent many woman from the extreme pain of child birth or the experience of going into labor at an unexpected, inopportune time.
The fact that elective cesarean sections are unnatural has no bearing on the practice, as modern medicine itself is unnatural, yet no one would claim with a straight face that we shouldn't use modern medicine. If people choose to have a cesarean section, there should be no legal hinderences on this practice.
The mechanism of birth squeezes the infant's respiratory tract, releasing the fluid build up and preventing respiratory complications. A cesarean section is a major surgery. All major surgeries carry significant risk, including an increased risk of hemorrhage. So if we're going by the ethical standpoint of nonmaleficence, it should not be ok to offer a procedure that poses significant undue risk to mother and baby when it is not medically necessary.