Indeed, Lessig has been less than totally radical but he's one of the strongest voices in the public discourse in FAVOR of cultural freedom. He wrote the book "Free Culture", he took on the entire government in the Sonny Bono Copyright Extension Act trying to stop the retroactive extension of copyright (he failed to stop it though), and he is the primary founder of Creative Commons.
You'd be hard-pressed to find a more respectable person when it comes to critiquing the problems with Copyright. Lessig is completely opposed to the copyright maximalists and deserves great honor for all his valuable work.