Firstly this study only deals with the Y-chromosome. This only affects the direct male line of ancestors. So racial mixing between Jews and Gentiles is not disproven by this in the least. It is possible for instance, that Jewish men moved to "Khazaria" and took "Khazar" women as wives and then rased their children as Jews.
For example, I bet that if someone did a Y-chromosme study of the mestizo population in Mexico the result would show that the mestizo Y-chromosome is very similar to the Y-chromosome of Spaniards. But this doesn't prove that Mexican mestizos are of the same race as the Spaniards and it most certainly couldn't be used to "prove" that the mestizos are actually racially "pure".
Secondly it doesn't give the statistics of relative purity with the Y-chromosome. Surely the purity is not 100%. So we can only conclude that the Jewish groups studied are genetically related in their male lineage. But we cannot conclude that they have a 100% pure male lineage. We cannot conclude that there was no mixing in the male lineage. And most certainly this isn't proof that Jews have not mixed with non-Jews.
The fact that mixing and conversions happened is self-evident just from looking at the lighter Ashkenazi Jews and then looking at some of the black African Jews.
It ain't bullshit, but it ain't what the arabs claim it is either. There is major evidence to support the theory that the Khazars were remnants of the ten tribes carried off by the Assyrians.
It's never over for the Islam first crowd and the Aryan nation types.