That's not what the study says. Christian Identity nuts are constantly misconstruing the facts. Ashkenazi Jews are about 40% admixed with Europeans, still 60% Middle Eastern -- the exact locus of the Middle Eastern part is all that is being debated.

Some quotes from the study itself that directly contradict the headline:

"Altogether, the findings indicated a remarkable degree of genetic continuity in both Jews and Arabs, despite their long separation and the wide geographic dispersal of Jews."

"In a report published elsewhere, we recently showed that Jews and Palestinian Arabs share a large portion of their Y chromosomes, suggesting a common ancestry (Nebel et al. 2000). Surprisingly, in the present study, Jews were found to be even closer to populations in the northern part of the Middle East than to several Arab populations. It is worth mentioning that, on the basis of protein polymorphisms, most Jewish populations cluster very closely with Iraqis (Livshits et al. 1991) and that the latter, in turn, cluster very closely with Kurds (Cavalli-Sforza et al. 1994)."

In other words, contrary to the headline, the Jews of today, though admixed, are indeed the descendants of ancient Hebrews. The Khazar hypothesis has been conclusively demolished.