People who don't know a damn thing about crypto see those ads with promises of easy money. Of course that only makes the rest of us look bad, so get rid of them. That way, the new money comes to the established tokens, like STEEM. Then they see how it works and rather than telling their 2000 Facebook friends about how they got ripped off, they start spreading the word about how things are looking good, because that was the only option the new money was given.
If Facebook and friends wanted to harm crypto, one way to do that would be to simply ban advertisements and let the crypto people panic, go into conspiracy theory mode, then spread the news like wildfire... wait, no, that's not Facebook doing that. It's the crypto kids. I'm even reading it in the comments on this post.
In reality, this is brilliant. If Mark truly was attempting to cause harm, he did just that by shooting himself in the foot.