The excessive surveillance was so shocking to the conscience that they will even allow child pornographers to go free. Bad guys on all sides, and nobody wins.
This is not "excessive surveillance". The person possessing child pornography put it on a file sharing service. Set its permissions to public and seemingly deliberately placed the files into a publicly searchable database.
This isn't even a case of a search engine finding things on a server that wasn't supposed to be exposed to the internet, Gnutella's entire purpose is to share files with other people. The fact that a government agent bothered searching this man's index of public files he intends to share with others is not an overbreach of his privacy. It would be like me putting my couch on Craiglist "Free couch at this address" And then a NCIS officer finding cocaine inside. It's not like the NCIS broke into every single person's house in Washington state.
The only reason this was overturned was not due to shocking surveilance, but because the officer who performed the search was in the military. The FBI should and can continue to perform these types of searches.