I don't use Facebook. But find this story concerning. Can law enforcement execute a
search warrant of your internet accounts without you being notified of the search? I think that's what Facebook's objecting to - not the warrant, but the fact that those affected aren't allowed to know about it.
Let's go a step further. Suppose an ex-spouse, disgruntled former employee, or neighbor down the street you're at odds with serves in some law enforcement capacity. Might they, under pretext, obtain a warrant to search & monitor your internet accounts without your knowing?
(Just because I'm paranoid doesn't mean they're not out to get me.
)
https://www.reuters.com/article/us-facebook-court-idUSKBN19O2IB