And now we come to the root of your self delusion. This is not an "inquiry of fact". This is not a "discussion of whether Bolt has doped". You have fundamentally failed to understand the subject of the thread.
If you read the subject line, this thread simply asks "why should we believe?" I gave several reasons why. I did not give arguments, but answers to the question of the thread. It does not ask "why should we not believe?"
You offer no facts about Bolt and no reliable method to determine clean from dirty. You only offer vague generalizations and logical fallacies, and "could have" propositions, to justify discarding principles such as justice, fairness, and unrecklessness. If that is good enough for you, that tells me a lot about you.
It is not doping and lack of testing that is undermining the credibility of sport -- it is the idea that, if doping enhances performance, that the opposite must always be true: all the best performances must be enhanced.
I'm not unique in this opinion. Here is a quote from a 2014 study "Prevalence of Doping Use in Elite Sports: A Review of Numbers and Methods":
"It is tempting to attribute outstanding performances to the alleged use of doping. The main problem with such a line of thinking is that the athlete will always lose in any such discussion: no matter how much he trains without the use of any prohibited substance, as soon as he excels he is, by default, a doping suspect. The essence of sport is to excel, and if excelling becomes synonymous with suspicions of cheating, each and every sport performance turns into an attack on the essence of sport itself. If such reasoning persists, this will seriously jeopardise the credibility of sport."
So there is another reason why -- this "line of thinking" "attacks the essence of the sport itself".
You began by raising the "presumption of innocence", which has no relevance to an inquiry of fact. You quoted the USADA to reinforce that position - which is also irrelevant to the same purpose. If speculation is what you are opposed to then, referring again to the example of Armstrong, there were years of speculation about him before his doping was proven. If passing tests isn't the measure, you offer no other standard by which you can confidently proclaim any athlete is clean. Indeed, by your introducing WADA and USADA into discussion of whether Bolt has doped you effectively score an own-goal, because the existence of both organisations points to their failure to change the general picture, which is that many more dope than are caught. That means Bolt also could easily have doped and not been caught. My views on whether Bolt doped are not based on your facile interpretation - I haven't argued them. It is your "smokescreen" attempt to close the discussion down that I take issue with. When pressed, all you are able to say on the substantive question of whether you think that he has doped is that you "can't tell". You should have left it at that. On that question, the rest of what you say means nothing.