Clearly, society does not have an ethical problem with experimenting on humans: we let companies do that all the time. Since it is only academic experiments that have to pass stringent ethics committees, it must be that what is prima facie unethical is learning useful things from experiments on humans. We have taken our cue from Genesis:
But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die.