Maybe passive isn't the right word? How about definitive? In stales speak, adverbs make a statement wishy washy.....

eg "Tall trees are generally found in valleys" is unacceptable to a scientist. The statement implies a lack of conviction as to its accuracy. They would be expected to write "Tall trees are found in valleys" or, if they couldn't prove this, they'd be expected to leave their pen capped until they established the facts.

Same example would apply for "usually", "actually", "really".

There's a politely heated thread on this somewhere in the archives....

Presumably you see what I'm really getting at?

stales