In order to make judgments without facts, we are best served to inform ourselves using statistics.
Rojo's logic is backwards because he misreads the statistics, claiming that someone who is statistically unlikely to be a good sprinter is nevertheless a good sprinter because of his unlikeliness to be a good sprinter (e.g. because they are an outlier).
That's like saying you are likely to win the lottery because your chances are so low.
If being tall were a revolutionary advantage in sprinting, Bolt might still be the fastest ever, but there would be strong evidence that height was an advantage which would show up in the statistics (i.e. the average height of top sprinters would be taller).
Leg length is not the important physical factor that makes Bolt fast. Bolt is fast because of his ability to generate power versus his weight. The reason other tall sprinters usually have lower turnover is because their ability to generate power is lower. Why is Bolt alone able to generate more power than all the other tall sprinters?
If Bolt is actually clean, it has nothing to do with his height, and is more likely to be a genetic advantage in the natural production of muscle building hormones. Bolt is actually competing at a disadvantage because of his height, and the statistics strongly suggest this.
Also, Bolt being a child prodigy proves nothing. Marion Jones was a child prodigy. Either they were both doping all along, or they both had the potential to be the fastest clean sprinter ever. Being fast as a youngster doesn't have any bearing on a person's propensity to cheat.
Since there is no evidence that Bolt cheated, I don't know any more than the next guy whether he is clean. But Rojo's logic is laughable and my judgment, based upon statistics, is that Bolt is more likely to be dirty than any other athlete in history.