I think it's a pessimism based on a realism.
There may be no legitimate reason to assume "natural" equals fruity hippy anti-science claims. But, unfortunately, the history of groups using the word "natural" in their name has more largely been hippy fruity anti-science people than not. So it gets a bad rap.
Not that there probably aren't exceptions, so don't go quoting to me some excellent scientific resource called Natural Something... I'm sure they're out there! But in my experience, anything calling itself 'natural' is normally unscientific.
Deb, in New Zealand