I can't count the number of times I've googled something, clicked on a promising result and immediately hit ctrl-f to re-search the resulting page for what I was looking for. Often it is either hard to find or not really there in general. Maybe its a link to somewhere else, or a partial text from another article, or simply 5 pages down due to a horrible layout.
Anything google can do to reduce this terrible UX is worthwhile.
If your primary business model is free content, ad supported, and rely on google as your search engine, you don't have much of a choice.
Right or wrong, your business model is Google dependent, and you are held hostage. If you don't like that, it's time to find another business model.
(Google being a monopoly is another issue, but no search engine is required to carry your content for discovery (yet, who knows what congress will throw at the wall next year))
There is nothing wrong with restricting the design of a webpage aiming for a good Google ranking: as long as it results in better websites rising in the results, it's a good thing.
Google's objective here is to reduce the ranking of bad quality ad ridden sites that attempt to serve as middle men between search results and a sale, low quality made for adsense sites. Anything google does to help rank these lower is good in my books.
The point is not that sites with ads at the top should be as high in the results as sites without ads, but that using such a high-level heuristic (as they claim) is a poor way to lower (or raise) the rank of a page.
Google could also do a lot more work to show you WHERE on the page your search occurs. That would do a lot more to address the problem than just lowering the rank of pages where your search is lower on the page.