Gossip protocol to find cheap routes for lightning payments makes sense because it's not being used to distribute human created metadata. There's no benifits to try and exploit this mechanism.
A gossip protocol to distribute lists of human curated relays, each and every one of them having an agenda, blatant or sublime, would be a disaster. It will be exploited because it can and will benefit spammers.
Letting people chose to use a relay that filters NSFW content has to be superior to forcing people to constantly be blocking NSFW relays they don't want.