The city just shut down a friend of mine last year ! he was warned over and over again , even his neighbors in the beginning were willing to work with him and they just got tired of being sick and tired . The police with the city halls help along with a few complaints from local neighbors in the hood , SHUT HIM DOWN ! FCC didn't have a damned thing to do with any of this. His antenna came down by order of the city or major fines were to be put in place within 30 days of citation given.
This is getting slightly off topic, but....
...It's highly unlikely that the FCC would step in and do anything to help protect the CB operator, even if he was running a 100% legal station. That's becaue they have basically turned over all enforcement of CB stations over to local authorities (cities, police, etc.). Unfortunately that means that local CB stations also may have little recourse if the local agency over steps it's authority or just plain "gets it wrong".
Keep in mind that this does not apply to other services that only the FCC has jurisdiction for enforcement over (business, amateur, etc.)
At any rate, good luck with trying to solve this problem. It really is best to work with your neighbors. As others have suggested, I'd start with filtering on his side if he'll let you, then work back toward your station.