It's OK if performance enhancers do just that - enhance performance. Only question that remains is fairness: some people with more money and better doctors will have the edge. Do you want sports to be a contest of natural athletic ability, or a pharmaceutical contest?
All contests are about finding the extra edge that the competition does not have and it's not limited to endurance sports. The teams that have more resources will always have a better chance of winning. The concept of "fairness" is an illusion. China tortures children from the age of 5 to find the winning gymnast. Western democracies can't do that. It's against the law so where is the fairness?
In F1, the bigger teams always dominate because they have the resources and expertise to squeeze out that extra 0.05 seconds in lap times. The smaller teams have no choice but to play a support role. Braun won the title 2010 because they found a loophole in the rules and exploited it with their double diffuser. Was that "fair"? Of course it wasn't but that's what innovation and creativity is all about.
In soccer, the rich clubs can buy the best players in the world. Those with less financial muscle languish in the relegation zone.
Fairness is a nice concept but it simply isn't reality.