Here are a couple ideas to contact Google and get their attention:
1) Email their press office (stating you readily found child pornography on one of thier searches should get their attention and with any luck, will at least route it to someone in the company who can get something done): firstname.lastname@example.org
2) Report it as phishing (they don't like this b/c it makes them look vulnerable to fraud and they WILL investigate it. They also have the ability to pull sites from their search engine):
3) Use Google's Webpage Removal Tool (must have a gmail acct or sign up for one, however):
Lastly, I have worked for and with the FBI, including internet operations. They would not post something so obvious as this in a sting operation. Most child predators are smart enough not to type in "child porn" and click on the first thing that shows up on a Google search. It is all black market, extremely clandestine operations.
Best of luck.