Choice quotes from the top three comments in that thread:
1) “To the extent that we expect agencies like the WHO to help us make informed, practical decisions regarding this sort of absolutist statement seems like an abdication of that responsibility.”
2) “The WHO is fear mongering. Maybe it is good health politics, people are scared of alcohol and people will have a better live. Maybe it would be better to communicate the risks more quantitavily. Not everyone is stupid.”
3) “The thinking is backwards on this. They state there is no scientific safe drinking level. They even compare it to radiation. The goal is to establish an unsafe level. it's like saying there is no safe speed to drive a car - sure that's technically true, but worthless to say.”
I think it’s just emotional reasoning and HN having a classic case of being critical when presented with evidence that contradicts your pre-existing beliefs while being uncritical of evidence that confirms them.
This is not true, at least with the WHO. Alcohol is a Group 1 carcinogen according to the WHO. It definitely causes cancer. The WHO classifies aspartame in Group 2b "possibly a carcinogen." There's some confusion over how to render uncertainty here, but the WHO does not actually classify aspartame as a carcinogen.