Replacement Theology

We have been going through the book of Romans in church, and yesterday we got to Romans 9:4,5.  I do not know the history of the movement, but the concept of replacement theology has sprung up in various places around the world some time in centuries past.  In case you are not familiar with the concept, replacement theology is the idea that since Israel did not nationally accept Jesus as the Messiah, God has tossed Israel aside, and replaced them with the church as His chosen people.  The problem is that this view is contrary to scripture, since it would require that God is changeable in His nature, and even a liar, since He made a covenant with Abraham and his descendants forever.  But even more than that, if Israel has been tossed aside for failing to listen to God, why is the church not also tossed aside, since the "church" has done as much wrong in the name of God as Israel has.  In fact, taking the crusades and other "religious" wars as well as the inquisition, the "church" has probably done more horrific things than Israel ever did, yet those who believe in replacement theology still believe that God will not follow the same standard He set for Israel.