Just in case anyone doesn't know, your follow list is completely public data on Nostr, and due to how decentralized SNS works, it is the type of data that is rarely but is recommended to be broadcast to almost all relays.
And this information is utilized for various purposes. The most common use is to act as a filter to screen out unpleasant spam. Since Nostr has no administrators (censors), a separate mechanism is needed to filter spam, and it's typically used to make an assumption like: posts by people who are followed by the people I follow are probably not spam, and so on.
If you still see an unpleasant image despite such filtering, it means someone in your follow list is following the spammer who posted that unpleasant image, which naturally leads to users trying to find out who that person is.
Of course, I know that following someone doesn't necessarily mean agreement, support, or affection for that person, but your taste can be questioned, so I hope you manage your follow list with a bit more caution.
If you feel those around you don't know this, please boost this so they can become aware without feeling awkward. Lol.
I should also check my own follow list to see if I've accidentally followed anyone