This will be my final thoughts on the subject as I realize there is separate forum for this.
The simple truth is, even without concrete proof those who insist he is dirty will never be convinced he isn't. Armstrong can never prove he is clean, and it's obvious many give him absolutely zero benefit of the doubt.
Pre-cancer and even in the first few TdF wins compelling arguments can be made on both sides. Beyond that, I look at motivations, and I think I've pretty well laid out why Lance simply has more to lose and reasons NOT to cheat than just about any other athlete out there. And if later tours are clean, it certainly throws plenty of doubt on the speculation of the early ones.
Yes, books and articles have been written, and Armstrong has won libel suits (or the defendants have settled) against most of those people. It has to be an almost completely baseless attack to lose a libel case.
And let's talk about this year. 37 or 38 years old, four years off the bike and he's competing to win the tour? You say he must be using again. That's such an absurd claim it borders on fantasy. Why Why Why? Why, after beating it all those years, why come back and risk it all? Why come back, at least partially, to raise awareness and promote his foundation and jeopardize all that? Why stir up the old witch hunts and go through all this again? Why risk a potential political career (I've seen speculation, I find it laughable). He's an icon that has transcended sports and it simply makes ZERO sense to come back to the bike and risk it all getting caught cheating. I find the contention that he's motivated more, or even equally, to win another TdF as opposed to building some awareness for his foundation and other causes to be laughable. Your idea that he came back and is doping again because he cares more about winning another TdF than everything else he has going on, when he's arguably already the greatest TdF rider ever, is patently absurd. No one really expected he could win, he just has to not embarass himself. Yet if he does finish on the podium, you'll believe he doped out of some inexplicable desire to risk everything for another victory (yawn, #8).
Believe it or not, the most logical explanation here is that freaks come along every now and again (Babe Ruth, Secretariat, Tiger Woods and Michael Jordan, to name just a few). And there's more to it than that, Armstrong's TdF-specific training and dominant teams.
Honestly, to not look at motivations and legacy when speculating Armstrong has doped all along is ignorant. To dismiss the extremely powerful incentives Armstrong has to NOT dope is to ascribe to him a subhuman level of ego, hubris and self-centeredness that is pretty much rivaled by only some truly nasty people in human history. That's where the absurd wild speculation comes in, because I think that's what it would take for Armstrong to ignore those incentives.
I simply think it unfair and irresponsible to assume Armstrong dopes because "that's what it'd take to dominate a sport with other dopers" while dismissing or ignoring the very real (and obvious) motivations and incentives he has NOT to dope. You've got a large amount of circumstantial evidence, a pretty good circumstantial case there actually, but you fail miserably when it comes to motive. And a lot of that circumstantial evidence has been contradicted or retracted by the accusers themselves, or proven false. Of course, the sensational press doesn't have as much to say about that.
Again, I'm going to leave it at this:
If the most tested and scrutinized athlete, the most vigilant athlete in defending his name, and the athlete with the most to lose is cheating, then there is not one athlete in the world that I will ever believe is clean.