Only human. That sums it up for me. Here's an Olympic Champion, a holder of multiple World Records no less, being held responsible for failing to be a role model for his avid fans and his adoring public, at the age of 23. That's terrible! Just because he does something that on one else can do -- and I'm referring to his ability to swim -- he should be allowed to explore his own existence; his life and time that he will spend on this planet. So, we have photographic evidence of him smoking some pot. So what? The poor guy made a public apology too, didn't he? I'm not going to go down the line of arguments like "biosterousness of youth" to make my point. On the contrary, I'm going to say that this is a sort of Jesus syndrome that people have; to sing praises and damn near worship a celebrity when they're doing well, but the moment something comes up, to be more than willing to nail the celebrity to a cross.
He's a kid and he loves doing what he does -- again with reference to the swimming. So, give him a break. There are bigger fish to fry out there. Like the drunk husband that nobody really cares about going home and beating his wife black and blue. Or, the paedophile traveling half a world away to engage in sexual intercourse with minors; human beings old enough to be his offspring. The list of injustices is immense, but we seem to find the time to crucify a poor kid who smoked some dope. So what if he turns out to be a dope fiend and quits swimming? You want him to win medals? Why don't you win a few? Why don't you try and be in the limelight for a while. Here's an article titled "What Michael Phelps Should Have Said" by Radley Balko, just to give you a feel of another way of looking at this.
I'm sure there are more than enough skeletons in your closet that other people would like to get a hold of. Let's stop pointing fingers at people who are just as human as us. No one asks to become a God, they're created by the people who worship them. And, they're brought crashing down to reality as easily as well.
Hey, at the end of the day, we're only human, right?