Beyond what I stated above, I'm not really understanding the argument of "fairness" when it comes to the use of performance enhancers. The "It's not fair to the guy who is natural and trains hard" logic seems a bit skewed to me. Many people are born with genetic gifts that others don't possess. I wouldn't say that's exactly fair. Of course, the retort would be, "But s/he was born that way... they didn't cheat." Okay, but that doesn't address the issue of fairness. So instead of fair, the argument shifts to "natural." Well, eye surgery isn't natural. Football kickers intentionally breaking their toes isn't exactly natural.
Words like ethical, cheating, fair, and natural are meaningless without being defined in the context of sports. The problem is, once you've defined these terms, you might not like how little they support your original position... or that there may be a lot more cheaters than you initially thought.