+100 on what Eden said. Starting with genetics there really isn't a true even playing field so this really isn't a good argument against doping - or at least not the only argument against it. That being said, someone probably won't be able reach that level of competition unless they have some genetic dice rolls in their favor to begin with - so leaving out the performance enhancing drugs does help to even things out.

Eden I love your analogy - I KNOW I couldn't out-ride Lance in those conditions, indeed I probably couldn't even keep up with him...