Regarding Mewtwo’s creation, in terms of what, anonymous? Granted, keep in mind that I’m technically not supposed to know anything at all about that event, nor do I actually know the intimate details beyond those shared among the members of the Symposium. So if you were referring to something specific about the process of its creation, I’m afraid I’m not privy to enough information to form an opinion.
However, the concept of a man-made pokémon—even a legendary—is an interesting matter of ethics. On the one hand, we already have perfectly sentient examples that no one really questions. (See voltorb, porygon, and so forth.) Likewise, being able to create manmade legends may give us the keys to understanding the actual, wild legendary pokémon—and thus, the primordial forces that influenced the shape of our world. On the other hand, however, one must ask if it’s at all right to play God and create life for the sake of science, especially if the aforementioned primordial forces of the universe are involved.
Therein lies the main issue with Mewtwo. Although we Symposium members only know as much as Professor Oak and his team have been able to gather, we do know that Mewtwo was the result of rather unethical experiments—ones that were less concerned with the subject’s well-being and more concerned with the effects of genetic engineering. Considering that, my personal opinion is that I feel rather sorry for Mewtwo, and if I ever came across it, I would most certainly like to befriend it.
As for ditto, I’m aware of that theory, yes, and I admit, it’s a rather compelling one. Even more than that, ditto isn’t a pokémon we have extensive historical records of—which is to say, researchers only knew about its existence recently, thus making the possibility of it having been created recently rather feasible.
The Pokédex According to Bill 