The ratio of Jews to non-Jews at the the turn of the start of the 20th century in the lands that Israel occupies were greatly in the favor of non-Jews. The majority of the non-Jews were of Arabic descent, though there were other sizable non-Jewish, non-Arab people there. This was the ethnic makeup of the land of Israel for many centuries. At one time, way way way way way back there, there was a sizable tribe of people calling themselves the Israelites that did the tribal things with the many other tribes that inhabited the area, fighting, killing, expanding, contracting, etc. The Israelites obviously did not establish a strong and lasting presence in the area. A presence yes, but the area ended up belonging (in the sense of being conquered and ruled by) to other tribal/ethnic groups. Also, the Israelites were not the first ones there.
Jews from around the world did not establish a sizable population again in the lands that Israel occupies until a movement started in the late 1800s among some Jews to establish a homeland. The movement was called Zionism and it chose what we now call Israel. Mass immigration started, and there was much conflict in various areas because sometimes there were more people moving into an area than there was land to support, and usually the Jewish immigrants won out on the disputes over who should stay and who should go. People that were living there for some hundreds of years sometimes were displaced to make way. This is the root of the dislike of Jews in the Arab world.
Much later, in 1947, the United Nations made a resolution to divide the area into separate Jewish and Palestinian states. The following year Israel declared itself an independent nation and was attacked almost immediately. Israel was prepared for this, as they had built up sizable military forces in preparation for such an event, took more lands, and the rest is history. Most of the Arab community does not look to Israel with much love for what they perceive as stealing Arab lands and feel helpless to do anything about it using force as Israel has more military power and an amazing intelligence service than do its Arab neighbors. Also, as the USA is one of Israel's major supporters both in the international political scene and in direct monetary and military aid, they tend to see us as "supporting the bad guy".
Basically it comes down to Israel took its land by force, keeps its land by force, and their adversaries in the area are pissed that they are too weak and inept to do something about it.
