If the content of the sites are the problem, well why would Google get a free pass on that point too?
The goal of the application itself, just like Google's, doesn't have anything to do with copyright violation, it just can be used that way.
Edit: Removed an irrelevant addendum.
If the image weren't a suitable representation, then the author wouldn't have chosen it. You're trying to downplay that these sorts of decisions are intentional.
Gun ownership is not a crime. But the gun is shown in a scenario where a crime is about to be committed.
At first I didn't have any issue but this analogy seems to have convinced me it's a bad image to use.
But I'm sure the maintainer will be happy to modify the picture with a search for "big buck bunny" if you ask nicely.
Edit: I'm not trying to be snarky or overtly pedantic, and the list of supported sites does suggest that this might be intended to facilitate piratism. Still, this is interesting and potentially useful technology, and seeing it merely as a tool for copyright infringement misses an important point.