Why Christians are desecrating Jewish Bible ?

The old testament prophesies about a messiah, which the Jews awaited. The birth and life of Jesus of Nazareth fulfilled all of the 60 prophecies (over 300 hundred references) from the Old Testament, which is why the followers of Jesus, and witnesses, believed that he was in fact the messiah prophesied about in Jewish scripture. In what way did Christians "claim" the old testament? It is what it is, Jewish scripture. The same God who inspired those scriptures including the prophecies, is the same God who brought the prophecies to p, and who inspired the scriptures of God's new covenant with us (as promised back in the old testament.) I'd be happy to teach you more if you're interested!