It has to be substantially true, actually; he had only to be a bit of a paedophile, had you had the information there.
The point that I am trying to make is that the person making the claim knows whether or not it is true. I know that I am a rotten scientist, and therefore to be able to make the claim I would have to try to find some evidence that I was a brilliant one, which might be a bit difficult. Asking someone to have to argue through the defences of the person against whom they want to take the action before they can start a case, if I have understood the amendment right, would create a higher hurdle for stuff on the web than for printed material, because the clause refers only to the web.