Jerusalem had been built and Jews lived in it long before the Arab "umma" was created: Islam is 1400 years old only, whereas the Jewish civilization is much older (you may need to check some secondary schools textbooks). As for the 20th century arrivals to Israel, there is one thing you may want to consider. About 18% of the Israel's population is comprised of people who had arrived from the former Soviet Union. There were called "Jews" back there and often discriminated. For that reason, they feel very strong attachment to Israel, both to the land and the country. Taking into account that they are pretty non-nonsense people in their political views, they hardly understand the concept of "political correctness". As Israel's patroits and soldiers, they are ruthless and adamant. I sincerely suggest you to avoid any discussions with them regarding "who and where came from", unless you have a strong urge to participate in Jerusalem-to-Arabia camel races (you may unintentionally reach the destination first, i.e. before the camels). Just a common-sence suggestion from my part. Good luck.
Israeli troops shoot, injure Palestinian crossing Gaza border fence (Haaretz)
from the article: 3 Lebanese soldiers, journalist killed in clash on Israel-Lebanon border