Does them performing this kind of intentional manipulation, and having such success, scare the shit out of anyone else?
Your previous efforts to police crafty humanss using AI has utterly failed. Just look at adsense and play store.
Even if you employed entire countries you still wouldn't stand a chance at reviewing it all.
Automated systems are the only way it can function at all.
Not in its current form. Google with all its might hasn't even managed to remove those "work from home for $$$" youtube comments.
Google doesn't have a good way to incorporate human intelligence (users) into its AI. Pure AI has no chance against an army of highly adaptable humans.
More to the point, machine learning is just building a model of what humans would do. Feed thing a million non-extremist posts, and a mission extremist posts, all of which have been manually marked as such by a human. Then ask it whether image 2000001 looks like the first million or the second million.
Using your metrics, it's just better for Google to turn the service off to free uploads.