Credibility of the WHO is a factor, remember that this is the org that blew swine flu and sars waaay out of proportion. They publish or perish. So it should come as no surprise that the causation is not even close to proven in their study – it is at best loosely linked.
Don’t even begin to compare that to smoking, which has been proven beyond possible doubt and was conclusively demonstrated in the surgeon generals 1962 report.
The WHO should be condemned for its irresponsibility.