Well, how would you define a cheater? And do you view cheating as being a good thing or a bad thing? Would you like to compete against a cheater? Why or Why not?
2. You state that doping (I assume this to mean using Performance Enhancing Drugs) should be legal in professional sports.
A completely different discussion. Using PED's would have to be legal before it could be allowed by sporting organizations. Having PED's legalized in sports is putting the cart before the horse.
But, just because a person (whoever it is) opines that PED's should be allowed does not withdraw the fact that PED users are, in fact, cheating, breaking rules, breaking the law (<--kinda important), acting against the integrity of the game and competition, etc.
They are viewed in a negative light because they willingly break the rules to gain a competitive advantage over those that follow the rules. It's really that simple. Certainly if a co-worker cheated themself into a promotion instead of you, or a student cheated themself to a scholarship that your child was competing for, perhaps your perspective would be different.
One could suppose that "everyone is cheating, so no one is". But, that's likely not the case. There are likely people within a sport that actually do follow the rules.
If the doping were legal, but regulated, there would be a more level playing field for all.
How would it be "more level"? ... and how would they regulate it to be more effective than it currently is? You make it sound like no one would go beyond regulations ... as if former cheaters would start following the rules. Nothing in that statement makes any sense to me.
-- Every morning brings opportunity;
Each evening offers judgement. --