Google is a private business and they can do what they want, but this disappoints me. More and more Google seems to be thinking of themselves as content police (consider YouTube is owned by Google also), and I think that's a shame. Perhaps it will open up a market for dethroning them. A serious YouTube competitor that doesn't demonetize content they find disagreeable would be very healthy, IMHO.
Can user sue Google if they follow an crypto advertisement on it, invest in it then find it is a fraud? It is likely self-protection.
It certainly would still be extremely unlikely that a victim would be successful in suing Google for damages of a trap they stepped into due to Google-supplied ads (just imagine what that would mean for kickstarter...), but chances of getting caught are not the line between right and wrong.