Everything.
I, personally, find it disturbing. But if it does not breach the ToS of the Android market, Google has no right to remove the materials. More than that: by removing it from the market, Google would be dictating the terms for censorship in the marketplace, making it difficult for neonazis to find material that appeals to them.
And this is a delicate issue: if you segregate against those with unpopular points of view (the neonazis, religious nuts (aren't them all), proto-terrorists, extreme right-wingers) you drive them underground. If their ideas can no longer be debated in the open, they will be debated - and reinforced - in communities with like-minded people.
I don't care about neonazis and other miscellaneous idiots, but I care about a functioning society I am part of. There is not that much difference between segregating on beliefs and segregating on skin color.