Let's examine the historical record.
First some background:
"Palestine" (the Latin/European name for Eretz Yisrael, the Jewish homeland) had first been partitioned in 1922-23. The eastern "half" (78%), located across (trans) the Jordan River, was made into an exclusive Arab state (no Jews allowed). Trans-Jordanian Palestine gained independence in 1946 as Trans-Jordan and (after seizing territory west of the river) would rename itself simply as "Jordan".
The western "half" (22%) was allocated to a Jewish homeland and it is this "half" that was again partitioned (this time by the UN) in 1947. The UN Partition compromise (UNGAR 181) gave Jews 54% of this 22% (i.e. 12%) of the land - 85% of which was the Negev desert. Jews constituted the majority of the population here.
Under the plan, the other 46% of the Jewish "half" would become another Arab state. Jerusalem (which also had a Jewish majority) would remain an international city, not part of either state but with free access.
Upon the passing of this Resolution, the Jewish Agency accepted it and Jews danced in the streets.
Rejecting compromise, the Arab reaction was very different.
Arab League Secretary, Azzam Pasha (16 Sep. 1947):
The Arab world is not in a compromising mood. It's likely... that your plan is rational and logical, but the fate of nations is not decided by rational logic. Nations never concede; they fight. You won't get anything by peaceful means or compromise. You can, perhaps, get something, but only by the force of your arms. We shall try to defeat you. I am not sure we'll succeed, but we'll try. We were able to drive out the Crusaders, but on the other hand we lost Spain and Persia. It may be that we shall lose Palestine.
Note the comparison of "Palestine" to other conquered and lost Arab colonial acquisitions (Spain and Persia) as well as the admission that the UN partition plan was "rational and logical".
They didn't really imagine that they might "lose 'Palestine'", thus once they did the cavalier attitude disappeared and they became hell-bent on its reconquest.
Trygve Lie, the UN Secretary General:
From the first week of December 1947, disorder in Palestine had begun to mount. The Arabs repeatedly had asserted that they would resist partition by force. They seemed to be determined to drive that point home by assaults upon the Jewish community of Palestine.
John Bagot Glubb, the British Commander of the Arab Legion:
Early in January, the first detachments of the Arab Liberation Army began to infiltrate into Palestine from Syria.... They were in reality to strike the first blow in the ruin of the Arabs of Palestine.
Note his reference to the "Arabs of Palestine", not "Palestnians".The UN Palestine Commission reported to the Security Council on 16 Feb. 1948:
Powerful Arab interests, both inside and outside Palestine, are defying the resolution of the General Assembly and are engaged in a deliberate effort to alter by force the settlement envisaged therein.Jamal Husseini didn't attempt to hide the known truth when he addressed the Security Council:
The representative of the Jewish Agency told us yesterday that they were not the attackers, that the Arabs had begun the fighting. We did not deny this. We told the whole world we were going to fight.
Andrei Gromyko, the Soviet delegate, told the Security Council on 29 May 1948:
the Arab states... organized the invasion of Palestine.On 15 May 1948, Arab League Secretary General Abdul Razek Azzam Pasha explained the Arab intentions:
a war of extermination and a momentous massacre which will be spoken of like the Mongolian massacres and the Crusades.
The Arabs rejected compromise and peaceful coexistence and started the war.
Not to defend Arabs but to "throw the Jews into the sea".