I think people are missing the point of why God selected the Isrealites in the first place... they were selected, not because they were special, but because Abraham was Gods friend. God chose Abraham to bring the Messiah into the world for the purpose of saving 'mankind'
He was not merely saving the descendants of Abraham... he was saving the whole of mankind. If the Jewish people or any other people dont want that salvation, then God is not obligated to them. But the fact is, the door is open to EVERYONE and no one has 'ownership' of God, so all this angst about not being the 'chosen people' anymore really doesnt make a lot of sense.
No nation is more special then any other nation.
Jesus was put to death because the people who killed him were murderers and full of hate, pride and bigotry.
There was no justification for murdering an innocent man and they were acting against the law of Moses when they put an innocent man to death. Their lack of fear of God is astounding and those who support their actions should ask themselves why too support the murder of an innocent man. One of the 10 commandments is "you must not murder" Anyone who thinks its ok to do so does not have God or his righteousness in their heart.
Jesus proved that he was speaking from God. He had miraculous gifts to prove it...just as Moses was given similar miraculous gifts to prove God was with him.
Jesus prophecy about the destruction of Jerusalem came true less then 40 years later... The fulfillment of that prophecy should have sparked a major shift among the Jewish people back then. That was a clear indicator that Jesus really was the promised Messiah and they should have repented and put their faith in him as God wanted them to.
God has never forced anyone to believe and practice obedience to him. But he has certainly shown his willingness to cast off those who reject him and his messengers.