Maybe Google is Evil is the wrong verb form — it's more a question that Google has become evil.
First, and from a practical point of view, it's (now) evil because we turn unthinkingly to it when in fact we would find better, more authoritative information somewhere else, and a lot faster: if it's something for your class, ask your tutor, or look in a book, or go not to a search engine like Google-is-Evil but to a portal like TeachingEnglish.org.uk.
So, to some extent, we've allowed it to become evil.
Apart from that, Google is Evil because it has become so important to businesses. As a result, businesses have stuffed the Internet with junk — simply so that their websites turn up top in Google (and other search engines). So a lot of what appears "top" in Google is in fact junk. Look carefully at what sites appear in the top 20 or 30 results for any search that is of "commerical value" and you'll see what I mean. How many of those sites exist simply and solely to drive traffic to other sites…? A lot…!
And because Google earns so much of its rapidly increasing revenue (99%, according to some estimates) from advertising, and now has to answer to shareholders, does it care if its results are stuffed with crap? No — Google is like television. TV stations really don't care that what they broadcast is garbage, so long as their advertising revenue grows.
Also, Google deliberately sets out to pretend not to be Evil: "Do no Evil" is its corporate motto. You have to be deeply suspicious of a company that sets out to dupe its customers in that fashion. It also says that its mission is "organizing the world's information and making it universally accessible and useful": the first four words of that make me highly suspicious.
Google is Evil because it steals things from people — from publishers and from anyone who owns a website, images for example.
Is Micro$oft Evil? Yes. Google is Evil for exactly the same reasons… and one additional reason: it deliberately seeks to con you into thinking that it is not.
"What is Evil?" I read someone saying the other day. "Evil is anything Google decides is Evil". Now that's worrying…!