Consider this analogy: Just because the DA doesn't have enough evidence to convict in a murder trial, that doesn't mean that the defendant is innocent. I just means they haven't been proven guilty.
Also, when you say "We tend to presume innocence", that's not really true. It's true (or is supposed to be true) for the government and people who want to be civically responsible, but a whole lot of the general population does not actually think this way. People think OJ did it, have various theories about who killed JFK, etc. People read the news about somebody accused of murder and think "yeah, that guy probably did it."
It's up to Meta to handle PR on such things. Unfortunately when your company is accused of, for instance, contributing to a genocide, your PR department probably doesn't have a lot of options.
Following from that, I can imagine a few viewpoints: 0) Parents are wrong, Facebook is awesome! 1) Facebook has violated existing laws (these lawsuits are exploring that space). 2) Parents should be frustrated with legislators for failing to regulate social media. 3) Parents should be angry with themselves for allowing their children to use Facebook's products.
I'm curious which (if any) of these viewpoints you hold.