Just because Palestinians never actually had a country called " Palestine " doesn't mean that immigrants can come in and kick them out. Wake up, it was called the British mandate for PALESTINE, not British Mandate for Israel. Did they just call it Mandate for Palestine because they liked the name Palestine?The Palestinians never ruled the country, the Jewish immigration was a result of international backing and British authorisation. The locals only began to call themselves Palestinians in the 1920's.
What Birtish authorisation? Did the British really own Palestine to say that their authorisation actually makes a change?
Let's say that, hypothetically, X nation occupies Israel in the upcoming few years and they give authorisation to all Palestinians around the globe to come back and enter Israel and establish a Palestinian state, will you as an Israeli agree? Even if they have international backing, you won't agree, never will you ever agree.