Well let's face it - Israel was established by the usurping of Palestinan territory.
Actually, it wasn't Palestinian territory - it was British territory.
Palestine - and, indeed, the whole of the Middle East - is the historic homeland of numerous Semitic tribes, both what we now call Jewish and now call Arab, but for the last 3,000 years has mainly been occupied by non-Semites. After the Assyrians (who were Semitic and forerunners of some modern Arabs) were defeated in the 2,500 years ago Palestine was occupied by Persians, then Greeks, then Romans, then Byzantines. After the rise of Islam over a millennium later, Palestine was ruled by Arabs - but not for very long, as it soon fell to Christian Crusaders, then Mamluks (originally from central Asia), then the Turks. After WW1, the whole Middle East (most of which had been occupied by Turks - again, not a Semitic tribe) was divided between European powers.
It's only been in very recent years that the whole region is run by the people who had been living there for thousands of years, usually under an occupying power. Most of Arabia is run by Arabs rather than Europeans, and the tiny bit of the ME called Israel is run by Jews. Both groups can claim it as their homeland, and both groups have the right to live there.
Some Leftie the Mitchel Bloke is - if Israel's justification is due to the fact that Palestine was a former British colony and later given to the Jews via the Balfour Delcaration, then maybe he should tell Africans and Asians of former British colonies are not entitled to their sovereignty, because their lands were British territories.