> You can see by the responses that this is quite controversial.

I don't think the tangent this discussion has taken is any indication that the original claim was controversial - merely that it's very easy to get bogged down in meta-discussions that detract from the actual issue being discussed. I don't think anyone could reasonably dispute the original statement - unless their interpretation of it was wildly different to mine. If that's the case then it's not lack of supporting evidence that's the problem - it's clarity of communication.