These all are just one sided claim by arab nations which is considered irrationale by world. UN didn't and never buy it.
Jews purchased properties from local arab in Palestine, not robbing or stealling as you guys like to accuse, it was documented and proven. During the nakba 1948 arab Palestine were not expelled but they had chosen to flee away and become refugee and as refugee they defied and said something bad against Israel government so Israel government didn't view them could be a good citizen if they come back, and Israel also received a lot of jewish refugees from arab nations.
en.wikipedia.org
So your fighting to resist is based on this claim which is considered ridiculous.
Arab Palestine had always rejected Israel peace offer and UN resolutions for the peace and chosen war/violence instead for their illegal claim. Unfortunately for them they lost and now they are crying for what they perceived as injustice.