You've invented a scenario that doesn't even make glancing contact with reality in order to rationalize your point of view. I'm actually on your side in this argument but not for this totally contrived reason.
The scenario is very real. Ad networks don't review ad content well enough, so scams and other malicious content are sometimes shown to users. This is also why the FBI recommends using an ad blocker [1]. Pretty embarrassing for Google that a public service announcement like this was needed.
[1] https://www.tomsguide.com/news/the-fbi-now-recommends-using-...