Steroids are very dangerous and pose inordinate risks to those who take them. It is very unfair to players who understandably don't want anything to do with these witches brews, to have to make the choice of either taking them or not being able to compete.
So to me, it is basically an arms race to get better armed than the next guy. None of this makes the game more enjoyable for fans, it is just a way of keeping up with the Bondses and McGuires and Cansecos and Palmeiros.
There has to be a level playing field for ALL players, that permits legal AND safe ways of boosting performance. Lifting weights and conditioning should be encouraged as positive player development.
A player should not have to face the decision to risk his future health and well being in order to compete with others who have already made the devils choice.
Can I tell you exactly what should be permitted (ie protein shakes, etc.) vs. prohibited? No, I don't have enough knowledge but others do. It is entirely possible to draw a firm line, what is permitted and what is prohibited, and have a robust enforcement effort to keep the game honest.
And when elected commissioner, that will be my most urgent priority (in addition to scrapping the DH, and re-aligning the divisions to be 6 x 5).