I sympathized with that line of reasoning much more before reading Thoreau's Resistance to Civil Government. Now I'm convinced that he should either resign or be held as equally complicit [1].
http://thoreau.eserver.org/civil.html
[1] He should either be willing to defend the current system, or he should stop being its agent. Enforcing a law brings the same moral responsibility as writing a law.
Timely, in another thread we are celebrating Google for ceasing to be an agent of the Chinese government. We should never allow moral actors to absolve themselves of responsibility by pointing to a far-away law.
From the link: "Thoreau’s love of nature and his advocacy of a simple life have had a large influence on modern conservation and environmentalist movements."
Beyond Walden, Thoreau's Resistance to Civil Government (also known by the title Civil Disobedience) has been cited as a major influence by civil rights leaders in the United States and abroad.
I don't think it'd be fair at all to say that Thoreau is forgotten in America, even if not everything about modern American life and culture conforms to what he might have wanted for the country.