Adjective vs. Adverb

It does make a difference for clarity, as this example from a morning newspaper today shows:

The brochures, sent to voters independent of Ballentine's campaign, championed Quinn's opponent as a defender of the environment.

So were those sent only to voters not affiliated with (independent of) Quinn's campaign?
Had the writer used -- or the desk caught -- this and used the adverb, no confusion for the reader:
The brochures, sent to voters independently of Ballentine's campaign, championed Quinn's opponent as a defender of the environment.
I won't say it's common, but I am seeing more of this misuse lately, just as in an earlier post I lamented the increased use of the descriptive for the adjective, as in this general form (a similar hed was seen in a recent paper): China consumers value Japan products (make it Chinese and Japanese).