Until fairly recently, I was naive on the doping in cycling issue. Different now, though. I've just finished my fifth consecutive book specifically on doping, or touching on doping in cycling and have to say that I trust very few of the current pros on the circuit, having availed myself of the available information on the subject in the sport. Examining the rationale for the existence of the books I've read shows differing reasons for their publication and most certainly no concerted effort to expose the pharmaceutical abuse issue in the sport.
From what I've read, I'd say the last TdF winner we KNOW to be clean was....Greg LeMond. Yes, it was pretty much that far back and we absolutely know that even prior to him there were many doped winners.
One known clean rider who comes out as being vociferously anti-drugs from the 'golden age' was Charlie Mottet and I'd like to see an award named after him. I'd like to see more riders strive to attain outstanding results on natural ability allied only to training regimes and nutritional intake like Charlie did.
I care nothing any more for those 'golden boys' who leave you full of admiration and wonderment at their performances only to be later revealed as being more successful at beating the testers than the terrain. In future, I'll watch the big three tours as travelogs showing magnificent scenery and revealing the history of the places en-route.