Looks like it's time once again to smack around some nincompoops.
"Hating on"? Okay, that crap has got to end, it's tired and played-out and if you use it then you're lazy in the head. I can believe something, like say Bekele will lose tomorrow, without having anything against (or "hating on") Bekele. Follow?
You're godd@mn right that nobody can "prove" that someone else is doping, what a keen grasp of the obvious you've displayed here. If they could, wouldn't they just take it up with WADA or USADA rather than with Captain Obtuse on Letsrun.com?
Get this: anyone is allowed to BELIEVE that anyone else is a doper and say so. It is not incumbent that the person who states that belief post evidence to convince anyone else of that belief, including jock-sniffer fanboys. On the same token, you don't have to like that belief and you're free to disagree. You're allowed to hold your own opinion on how much merit that belief holds just like that person is allowed to believe that way and voice that opinion.
Just don't try the dumb ploy of claiming that an athlete's claim with no proof while castigating someone else's claim that the athlete's dirty with no proof. You're both equally right or wrong in that scenario.
There's one other possibility, that the person has insider information (possibly from biased sources, possibly from credible sources) regarding the fact that the athlete is doping. How in the hell is someone supposed to present "proof" to you in that scenario? Is demanding evidence until you're blue in the face going to make it materialize? Hint: no. Another hint: many of us had knowledge that Marion Jones, Regina Jacobs, Tim Montgomery, and many others had been doping before the authorities came down on them. There ARE insiders (or people who know insiders) who visit this site, believe it or not.