I really don't get how the WHO gets to keep those lists without a severe backslash to their image. Since positive proof that something does not cause cancer is nearly impossible, both state basically that "a lot of people think those could cause cancer, none got to see any, be wary".

But walking outside in a sunny day is in a completely different category. Your comparison at the end is severely unbalanced, the Sun alone overwhelms everything else on both sides by a huge margin.