Doping would make sport more interesting
The benefits of doping in sports, on an entertainment level, vastly outweigh the potential disadvantages. Who doesn't want to see stronger, bigger, tougher athletes compete? Sports are, after all, designed to display many facets of peak human physical condition, and doping just ramps that higher and higher to the upper limits of possibility.
Watching bigger, stronger, faster humans playing sport would make for a better spectacle.
Competition at the highest level offers an unmatched display of athletic ability. This natural skill coupled with performance-enhancing drugs would make sport more interesting and entertaining to watch because of the superhuman feats and elevated fairness among both biologically gifted and disadvantaged athletes that would result from the use of doping. Allowing performance-enhancing drugs in sport would lead to smashed world records as stronger, faster competitors with more endurance enter their disciplines.  Watching the best of the best reach new heights in pursuit of their heavily coveted goals would catapult sport into a never-before-seen stratosphere, providing greater entertainment for years to come.
The excitement in sport doesn't come from the physical attributes of the competitors. It comes from watching humans push the natural limits of their body. Competition in sport is not based upon who can inject the most steroids into their body, but who can outperform everyone else with their talent, skill, natural ability, and hard work. Entertainment should not be so easily attributed to who can hit the most home runs or who can barrel down the competition with brute force; it emerges from the two best teams or individual competitors going at it. Doping removes this element from sport, and makes sport less, not more, interesting.
[P1] Bigger, faster and tougher athletes make for a more exciting competition. [P2] Doping makes players bigger, faster and tougher. [P3] Therefore, doping would make sport more exciting.
Rejecting the premises
[Rejecting P3] Part of the excitement comes from watching humans push their bodies to their natural limit. This would be lost if doping is permitted.