runn, you know nothing of the law of defamation.
We randomly test athletes, with no particular suggestion of doping. We test them as a condition of their participation in sanctioned events.
The testing, such as it is, provides evidence of either the presence or absence of doping, within the limits and errors of the test, custody, and security and reliability of reporting.
According to current rules, test results are not determinative--they are only one form of evidence that is used by a decision-maker, which evidence MUST be considered in light of the totality of the evidence. Remember, a test can be negative OR positive, and should not be determinative either way, and in fact is not.
An athlete is tested BEFORE they are ever caught. Does the act of testing impugn the athlete's character? Yes. Does the impugnment of the athlete's character rise to the level of defamation? No. Why not? Precisely because the assumption of a possibility of doping is warranted by the historical evidence.
If an athlete who wanted to compete in the Olympics for the USA did not want to submit to random testing as a condition for eligibility, they could probably bring suit in federal court on a constitutional basis. As far as the national federation and USOC go in the USA, the constitutional test used would probably be the "rational basis test"--you can look it up on the web. It is an easy test to meet, because the interest affected is not fundamental, and the class affected is not particularly a protected class.
The only way a challenge could possibly succeed, legally, would be to prove that most affected persons are of a particular racial class (e.g. African-American), and then show a constitutionally-unlawful disproportionate effect upon that racial class.
But the basic assumption, currently legally workable, is that an athlete cannot be assumed to be clean--they must be tested, at random, in the absence of any particular evidence of doping.
So, about all athletes including Bolt, it is fair game to say not only that he CANNOT be assumed to be clean, but that he IS NOT assumed to be clean, even by governing bodies and international organizations, to the judgment of which national organizations subscribe.
Bolt IS NOT assumed to be clean. Negative test results are some evidence tending to prove cleanliness at a particular point in time, but are not determinative, and must be considered in light of the totality of the evidence. Each person is free to draw their own conclusions, as long as their evidence is "legally colorable". The strength of their evidence and the quality of their conclusion need not rise to the level of that required of the governing bodies in order to avoid defamation. The bottom line of all of this is that there is a wide variety of defenses to defamation, many of which are satisfied by the normal and ordinary course of discourse on a forum such as this.
Furthermore, any statement must be taken not in isolation, but again in light of all the evidence. If a poster here in January says "Bolt is using", but in the previous July posted her analysis of some race results to "suggest that Bolt is using", the second statement must be taken in light of the first. And so on.
Not every disparagement is defamatory. Get a grip.
Finally, "Bolt is using". Do I have any direct evidence? No. Is there any contradictory evidence? Yes. Do I have any circumstantial evidence? Yes. Is it sufficient to be accepted by a governing body in imposing sanctions? No. Is the contradictory evidence sufficient to overturn the assumption that he might be using? No. Do we still assume that he might be using? Yes. Does my circumstantial evidence outweigh the contradictory evidence, in my opinion? Yes. Does my opinion matter? No. Is Bolt injured by my opinion? Maybe. Can he recover for any such injury? No. Is my first statement understood to be figurative rather than literal? Yes. Is it fact? No. Is it my opinion? Yes. Is it worth anything to me? Yes. Is it worth anything to you? You be the judge.