I’m sure FB does daily backups or snapshot backups.
So poisoning your data does no good for yesterday’s data as they can always restore your old data if they detect that your data was poisoned before your account was deleted.
Anything you post to the Internet is their forever.
ANTONYM REPLACEMENT
The most effective way to poison the Facebook data is with an Antonym dictionary. It would be irreversible and quite effective.
And yes, it could bring down Facebook permanently.
eg The cat ran well. > The cat ran bad. > The cat ran benevolent. > The can ran deserted.
Antonyms are divergent. Replace each word with iterations of antonyms.