Can anyone cite a precedent where Google used the front page for such an unquestionably political stance?

(I don't just mean political as in Democrat versus Republican. I mean an issue of great debate, overblown rhetoric, and one on which the public has, to some degree or another, actually applied pressure to achieve change.)

Here's the page you get when you click the black rectangle, entitled "End Piracy, Not Liberty":

https://www.google.com/landing/takeaction/

And here's the post at the Official Google Blog, by David Drummond, SVP Corporate Development and Chief Legal Officer:

http://googleblog.blogspot.com/2012/01/dont-censor-web.html

Read more about it by Matt Brian at The Next Web:

http://thenextweb.com/google/2012/01/18/google-goes-dark-in-protest-over-sopa-but-not-how-you-would-expect/