They're saying "this is what craft brewing is" and they're defining it as small, independent, with no adjuncts to "lighten flavor," whatever that means.
I fear it means they've gotten so hung up on trying to define themselves in terms of what they aren't that they're in danger of losing sight of what they are. There's a whole lot of great traditional beer that uses adjuncts to lighten the flavor. I mean, at the very least it's kind of hard to ignore that great big elephant in the room named Belgium.
Now maybe if they wanted to criticize the use of adjuncts purely as a cost-cutting measure in the interest of making cheap mass-market beer. But implying that it's anathema for one's explorations in adjusting the flavor of beer to stray outside the narrow lines of malted grain? Might as well try passing the Reinhetisgebot off as a "beer quality law" while you're at it.
(Edit: And a little more rant about their apparently strong conviction that using adjuncts in beer makes it somehow not "traditional." I'm a budding beer history nerd, starting to get into recreating historical recipes. Yesterday's brew was a first step in that direction - a mid 18th century Porter. Heck yeah there was adjunct in there. If it didn't have any adjunct, it wouldn't be what my great-great-great grandparents were drinking.)