Pure blood is meaningful huh?

[Magog]

After watching the Passion of the Christ I started to think a little. It is my understanding that Jesus was a pure blood from the line of David giving him authority to lead the Jews, and all mankind. Interesting that Pureblood was meaningfull. That not just anyone could be savior of all mankind, but only a pure blood Yuda, Jew. Racial purity is very important to the Jewish religion. We all know that the bible forbids a jew form marrying a non jew. Could this be in remembrance and/or obedience to the most high? That they are in charge with keeping a pure bloodline so that the savior, second coming or the first may enter this world and save all mankind? And if so, is it not seen as the work of the devil to pollute the blood lines of all people to make sure the savior may never come to work his magic? If not for this reason, then why was a person blood line held in so high regard and importance?