Ever since Google was a major ally of the anti-SOPA movement, and played a big role in stopping that bill, RIAA probably hates Google more than anyone, and they've been pressuring them into doing a lot of stuff for them already. Google, naively, actually thought that doing some of those things would "appease" RIAA, and they wouldn't bother them anymore.
How cute of them to think that - because it's never going to happen. RIAA will come back asking for more, and more. They never stop, and nothing ever pleases them. Google is also the biggest search engine that happens to index a lot of web pages, since that's their job, to automatically index web pages, but RIAA just says they are "aiding pirates", and that search ranking should either change so it suits them, or the links they don't like should be completely eliminated from the index.
Google must've made the initial deal with them in the first place (since DMCA doesn't really specify that links to pirated content is illegal) when they wanted to get all the songs from the labels, as well as other type of content. They even went as far as removing some search suggestions for torrents, and downgranking sites that receive too many DMCA requests. So basically just because you are accused of something, Google now treats your site as if it's already been found guilty. This is just one of the major flaws of DMCA, but in the same time it's also something Google has agreed to follow.
But as I mentioned, RIAA is not satisfied, and they want Google to do even more, and get rid of the links even faster, as if it's Google's job to solve all the world's piracy problems for them. Let's forget for a minute that RIAA is still trying to cure the symptoms instead of the cause of piracy (lack of availability worldwide, and not very affordable prices). But RIAA is still trying to make 3rd parties guilty by association, just like they tried to make ISP's guilty for "transmitting" pirated content over their network with ACTA (which fortunately failed to pass in Europe). If it were after them, search engines, ISP's, carriers, and all kind of other business would all be guilty by association for being even remotely related to piracy, and they should do all the piracy policing for them, with their own money.
I don't think RIAA to ever change its thinking, but I do hope it pisses off enough people and companies, that they start lobbying to repeal or amend DMCA to take away most of their power, and specifically the power to say that hyperlinking to "allegedly" illegal content is also illegal.