Sure there would. Most fans are aware that every Mr. Olympia competitor got where they are with the aid of illegal performance enhancing drugs yet the fans are still interested. Likewise, I would bet most fans of football, baseball, etc. are aware that many if not most players are on performance enhancing drugs and the interest is still there.
How many professional athletes (not including bodybuilders) can you name that doping has killed?
If you’re possessing and taking PEDs without a prescription (which is usually the case), laws are being broken. Was Armstrong found to not have broken any laws or was he just not charged with anything? Admitting to illegal drug use is not usually going to land anyone in legal trouble; it’s when you’re caught possessing them that you end up in hot water. He admitted to taking Erythropoietin and hGH. I doubt he obtained both of those compounds legally.
See above.