Sound like the question you're asking is "What was the Nakba and what happened during the Nakba?"
The very short version is that Zionist militias and paramilitaries used massacres and terror tactics to drive three quarters of a million Arabs to flee from their homes in to an exile that is ongoing to this day.
The person's statement that the people who left wanted to leave is completely untrue historical revisionism and genocide denial. Zionist military forces very deliberately enacted genocidal tactics to force much of the Arab population in the region to flee for their lives, generally with nothing. Massacre, rape, torture, property destruction, poisoning of wells, and all the other classics were used as tactics in pursuit of this goal.
It must be remembered that, especially by the forties, few Zionists had any intention of peaceful coexistence. Starting with Theodore Herzl, and stated very plainly by Zionists throughout the late 19th and 20th century, Zionism is a colonial project premised on the removal of the indigenous population. Zionist thinkers, writers, and leaders have generally been very frank about their goals and methods.
It needs to remembered that Zionist military forces had been engaged in terrorism and sabotage in the Levant, fighting against both the British occupying forces and indigenous Arabs (among others) since the 20s. The Nakba was not the first time that Zionist military forces had engaged in mass violence against Arab Palestinians. Also needs to be noted that, prior to the Holocaust, Zionists operating in Palestine generally did not have the support of indigenous Jewish Palestinians. They were a self-consciously outside group of mostly secular colonial invaders spreading terror in the region in pursuit of their own goals, and were recognized as such by everyone. Prior to the Holocaust giving them an entirely unearned veneer of legitimacy pretty much everyone - Jews, Arabs, British, everyone, viewed them as a terrorists. Sometimes useful terrorists, for the British, but terrorists none the less.
Look up early Zionist paramilitaries like Irgun, Haganah, LEHI, the Stern Group.
Onward to communism and/or anarchism!