But the majority of that online advertising income comes from ads on their own search results pages, not from adsense ads.
It's very rare that I search for a product and even then, chances are that I add "review" or "sucks" (can work fine in combination with a specific product; negative reviews often tell you more about a product than positive ones, just like a requirements document or a product road map becomes a lot better if one includes things that people might the product to do that it will not do)
Usually, the companies whose ads I'd want to click on rank high in the organic search results, anyway.
Heck even creating a credible enough rumor that blocking google search ads seriously degrades results could have a material impact.