So, if the Native Americans or the Australian Aboriginals rose up and started slaughtering their occupiers, you would consider it legitimate?
They would have legitimate claims according to you, unlike the Arabs that have only decided to identify themselves as Palestinians since the 1960's.
Most if not all countries rulers and borders have changed over the centuries, usually by war and conquest. The Arabs are indigenous to the Arab Peninsular. All other Arab countries in North Africa and the Middle East have been occupied by Arabs