Most drugs that this argument claims to be "safe" have serious mental and physical side effects on the athletes who use them. According to the USA DA, anabolic Agents like testosterone can result in "Increased aggressiveness and sexual appetite, sometimes resulting in abnormal sexual and criminal behavior, often referred to as 'Roid Rage.' Withdrawal from anabolic steroid use can be associated with depression, and in some cases, suicide."
In 1984, even before the steroid use in the MLB, six athletes across various sports in 1984 were killed by anabolic steroids. 
The negative effects of such a proposal outweigh the positive ones, and simply because that industry is better regulated does not mean there will not still be underground practices that can seriously harm an athlete. There should not be a debate on how detrimental these drugs can be to the body.