A Jew to a Kill

AITOOW wonders why the term "Christ killers" is a bad thing? It should be a good thing or at least a push. Wasn't Christ's dying why he was placed on Earth to begin with? Wasn't it the requirement for the cleansing of our sins? If the Jews (it was the Romans/Italians who put him on the cross but let's ignore that fact) "killed" him, shouldn't we have been thanking them this whole time? No Jews, no crucifixion, no happy ending.