Natural and normal can both mean the same thing, and not the same thing.
In the sense of normal meaning the most reoccurring thing, then natural doesn't have to mean normal. In the example I said above, green eyes are not normal in the sense that they are the most reoccurring, but they are still natural.
Then there is normal in the sense that it happens without intervention from a sentient or otherwise unlikely outside source. Homosexual fits this description. In this sense, homosexual is still natural.
Nature doesn't give a crap if you enjoy surviving, your instincts don't care if you're happy while doing it, it just wants you to do it. One Piece is extra. We, as human beings, have figured out this concept. We are entitled to indulging ourselves in it.
Humans aren't supposed to do a damn thing. We do what we want. That's what being human is. If we just go by instincts and what "nature wants," then we should have just stayed neanderthals, simply as that. This whole "It's not the design and masterplan" bullshit needs to end. That ain't what we are.