I really think the only solution is "don't put google AI summaries at the top of every search".

AI tools are notoriously unreliable, and people that use them *on purpose* generally know and recognize that. If grandma, who is not super-internet-literate, types a query into google and gets a phone number, she's going to assume that it's the correct number and not the result of a lossy data store that's under active (and constant) attack.

It used to be that you could reasonably verify your source with an HTTPS cert (so you can probably trust the number that's on Delta Airlines' website), and pop up scary warnings for grandma if those certs failed. Now every piece of misinformation has a valid cert from google or meta or X, so determining the truth is much more difficult and time consuming.