Speaking as an outsider, I think the horse-racing world could learn something from the experience of Lance Armstrong and bicycle racing.
Armstrong spent much of his career excoriating those who accused him of doping. He called the competence of drug-testing (and the people doing the testing) into question, he lambasted former teammates who claimed to have seen him injecting performance enhancing substances into himself (basically suggesting that they were jealous of his achievements) and, apparently, he justified his use of drugs by stating that “everyone did it.”
He and the other cyclists who doped called the banned substances by various pseudonyms, as well as stating that they were vitamin supplements, etc. to deflect criticism and detection.
When he finally had to admit that he had in fact been doping, it not only destroyed his career, it tore the sport (and its fans) apart.