“Websites dedicated to trafficking in counterfeit products and digital theft dupe consumers, steal our jobs, and threaten the vibrant Internet marketplace,” said Thomas J. Donohue, president and CEO of the U.S. Chamber. “We commend Senator Leahy and the bill’s cosponsors for introducing this critical legislation to address the growing threats of counterfeiting and piracy over the Internet. Addressing this problem is a win-win-win—good for businesses that need to protect their IP online, good for America’s economy and jobs, and good for consumers who will benefit from both.”
The Chamber is also a sleazy, underhanded organization discovered to be running its own covert propaganda and cyberwar operations against groups that oppose its political positions. Like, say, Anonymous, which uncovered the weaselery.
Hence, Anonymous doesn't like the Chamber much, or the vigor with which the Chamber has been promoting and campaigning for what Anonymii -- and a good number of simple Americans who are able and willing to read the definition – consider to be a violation of the most basic Constitutional right – the right to speak.
You can understand the venom behind Anonymous' response, even if its solution – aside from being illegal and inconsistent with arguments in favor of free speech – is a little lacking in subtlety.