A specious argument. There has been a territory called Palestine for 2000 years and its inhabitants are rightly called Palestinians.
Actually, they are immigrants (illegal?) from Iran, Lebanon, Egypt, and elsewhere...
False. Genetic studies have shown that the Palestinian Arabs are indigenous to the territory and are distinct from Arabs from those elsewhere in the Middle East. But even if they were immigrants, does this not hold a fortiori for the Jewish immigration after WWI and WWII? Why would a Jewish immigrant be legitimate but not an Arab?