Also, there is more going on here than just speech. The Constitutional guarantee is absolute only in that government may not exercise prior restraint or prosecute publishers for content, and no one is denying his right to publish what he obtains legally. However, receiving stolen goods is not protected, and the leaked documents were stolen. The First Amendment is not a license for the media to break the rest of the legal code in pursuit of a story.
Finally, Wikiboy isn't a US national; he is governed by Australian law and the laws of the nations in which he operates. The Commonwealth has a very strict official secrets act and he could be prosecuted under that.
We agree on Manning, and I want to see him prosecuted for, among other things, treason. However, while he is solely responsible for the leaks, Wikileaks is an accessory after the fact, in that they took possession of stolen documents, disseminated classified information during wartime and aided and abetted al Qaeda and the Taliban. At the very least, this last makes them an enemy combatant.