You're missing the point. Here's a scenario for you.
It's 2200. Israel has long since conquered every bit of land that was once Palestine. Despite this, the nation of Palestine lives on, without a country. Through 200 years they have been able to maintain their national identity despite living in various countries around the world. They now turn to the UN, pleading that this piece of land where Israel now is "was promised to us by the holy lord

".
Now this may actually happen, it doesn't seem all that unlikely. And in your opinion the UN should tell them to gtfo, right?
Here's the key question. If I ask you in 2200: Does Palestine have the right to exist? What do you say?