If we look at this objectively then can we really blame them? Go look at twitter with all the "Send me 1 ETH and I send you back 10 ETH" scams.
A lot of people are getting scammed, mostly new people who don't understand the first thing about the technology.
Unfortunately this move won't stop the scammers you mentioned.
Those are normal users, they don't really buy ads for their petty scams, and they will continue to pray on gullible victims.
I would really want to see more from all those companies that claim they are acting against fake ICOs that is not just banning stuff ads while letting the sharing spam go unpunished.
It wouldn't hurt them to add a small alert line when you open a page that contains terms like ico, investing that would lead to a tutorial about the risks of investing in a shady scheme.
Education is the key and it would be far more efficient than a ban.