From a business perspective this is a bad choice. I'm not advocating showing holocaust denial either, but this got them in a very bad spot: they've set the precedent that they curate the truth. This opens them up to all sorts of curation demands.
AGAIN, google's goal is to organise all knowledge and that's exactly what it's doing. That holocaust denial is a thing is also knowledge, and so you can find it by typing "holocaust denial".