Yes, hardforks can destroy data. I cover this in a comment below. Yes, right to be forgotten laws apply to here too. I see Google lost the case.
A vast majority of Steem witnesses and nodes operate out of Germany. It has strong laws on a lot of these topics, and I can assure you there's thousands of posts on the Steem blockchain that blatantly violate EU laws.
PS: Witnesses should probably consider moving their servers to jurisdictions with lax legal systems at some point. Moving themselves too, for that matter.
PPS: Further on that, there could be a moderation system where posts reported by authorities or citizens can be put forward to top witnesses to vote on for removal. If ~15 (don't remember the exact number) of the top 20 witnesses vote to remove some content, it'll lead to a new fork. That'll lead to thousands of forks, and in general seems like a messy situation. Just thinking out loud here.
There are definitely a lot of challenges a decentralized community is going to face and some (like this) are going to have massive ramifications and require large concessions to authority or changes in legislation by the authorities to accommodate it.
While we are in infancy mode and they are playing catch up, there is a chance that foundational developments can be made and as people globally pour in, we are able to force legislation changes. If too many keep bickering for too long as they look for short gains, the authorities will move before the chains and shut and lock the floodgates to stop the onboarding needed to tip the scales in the favour of people over government.
The question is, can we come together before they circle their wagons?