I was going to write basically this comment but had trouble expressing it coherently. However, I think there should be an (optional) filter on search results to prevent mature results being returned accidentally. There's no point trying to stop kids seeking out this kind of content if that's what they're looking for (a losing battle if ever I heard one), but like the example given in the article - a search for 'Human Male' shouldn't give results any more inappropriate than you'd find in a physical encyclopedia.