The thing is, if some relay is trying to stop you from saying what you want to say, you can always look to a different relay until one will let you say it, but once it's said, there's no telling how many other relays have received a copy of that message.

You can say you want a note deleted, but unlike Twitter where they have a single copy of that record (duplicated across all of their databases) and can definitely that they've "deleted" the master copy of that note, in nostr, each copy on every relay is the master copy of the note with all the bits required to prove that you wrote it and it hasn't been modified. Those relays are under no obligation to process your delete request but even if they did, there's no way to know that someone didn't copy the json to notepad or something. That notepad copy is still a legitimate version of that message. Way better than a screenshot.

This is why clients try to set the expectation that they will try their best to make sure it's deleted, but once somethings out on the internet, it's hard to make it disappear for good.

No one has to listen to you. The event is out there now and all you can really do is tell people to ignore it.