We have personally disabled social media integrations. It's become more of a hassle than it is worth honestly. Between changing their rules/policies on the fly without proper notification and the how they are making integration and compliance harder, it's just not worth it anymore.
There is not a general policy that can be copy/pasted... it's something you need to explain for your community. What data are you collecting? For example, do you require more than just an email account to create an account? When someone requests their account be deleted, what do you do? Do you just anonymize posts made or do you fully delete anything ever posted by them? Are you using the new built in account delete feature?
This is more to explain how YOU handle your site. But again... I would suggest telling Facebook and the rest to take a hike.