Generally speaking, there isn't a right to force others to delete stuff you've posted to the internet - only stuff related to PII. If you anonymize posts (say, change the username to AnonymousCoward and delete real names, reset passwords, etc), you're 99% of the way there - and if the person in question comes back and says "you've not deleted PII that I posted in one of my posts", you can go and delete that or edit it out, you're not about to get fined if you make a best-effort attempt as a small company - only if you're obviously negligent.

There is no right to delete stuff that is not PII.