Dunedien
I feel like it is all a version of fiction. It is not real, so if you want there to be genetic engineering, then sure. If not, that's fine too.
I generally agree with this, but when you're working with specific, pre-established genres, it's not always the case. When you're writing or working with fiction, sure, you're free to do as you please, but you have to accept that people may disagree with your use of certain elements.
We've all seen (or heard about and avoided) what Stephanie Meyer has done to the fictional concept of Vampires, and people either love her, or want her to suffer for a thousand eternities in the most agonizing, excruciating torment beyond possible human imagination.
I think most people would like to avoid such controversial "genre raping" as I like to call it. Most authors and creators aren't willing to piss people off, because pissing people off, while excellent media coverage, is not the best way to attract people to your creation. So few people are open-minded enough to say, "If you want to do it, cool, but if not, that's cool, too!"