Really? I've done some serious day hikes in severe weather (snow/constant drizzle/heavy rain/wind) wearing 100% cotton underwear, shirts, jumpers, and trousers (everything was cotton except shoes and jacket) and never ran into any trouble with it whatsoever.

I also have some merino layers and when i have worn them in the rain and cold its not like theres anything magic about them. Maybe the cotton was slightly more uncomfortable and stayed wet slightly longer, but I never felt in any more danger with the cotton than with the merino.

Is the anti-cotton thing just for people spending multiple days in the wilderness?