"That[present links to back up assertions]'s been a clinic rule for a long time."
No, it hasn't. It's in the guidelines. And it certainly hasn't been interpreted stiffly for as long as it has been there. For reference:
"Proof of point, opinions, and common knowledge: you can't just say "we know Bobby the Bod is doping". You have to provide some proof using linked sources or verifiable material. Or, you can just state "in my opinion". If, on the other hand, it is in the realm of "common knowledge", then it is acceptable to make an unverified statement. Be careful - common knowledge would apply, for instance, at the time of this posting, to Lance Armstrong. But allegations of current doping, and current riders, would not be "common knowledge" at this point. To be common knowledge, the "fact" has to have been published, widely read, and widely agreed with. This point is particularly applicable in The Clinic."
If you take it literally, then (if it was a rule) you'd have to enforce it every single time a rider, who hasn't been sanctioned (or the fact that they are doping have been "published, widely read, and widely agreed with"), is asserted as a doper. It doesn't happen.
...
Now, I haven't followed the latest Froome motor discussion, but wouldn't it be fair to assume that some (probably a fair share) of the "assertions" would (indirectly) fall under the "Or, you can just state "in my opinion""-clause that is written in the guidelines? I do get that some posters (like thehog) like to state opinions as fact, but it is my experience that the vast majority writes in a way where it is easy to read that it is not an absolute truth, but merely their point of view.