Yeah I see.. there's where paid Relays, or the ones like Damus has, help to prevent that kind of spam.
Not sure if there is a solution for it.. public relays are just like public squares, everything can happen, there's no State or Authority that can block it.
Probably that's how global should be, and we should create tools that permits us to navigate every realay with the possibilities to unsee what we know we will not like..
Maybe in the future we can choose an AI tool that will read images and analize if there's content you chose not ro see and will block it for you before you read the note.. so there's no manually block, the tool already knows what you do want or not want to see.