Granting United Nations membership to the Palestinians would create a vary dangerous precedent. The Palestinians aren't the only ethnic group that desire to have their own country independent of the one in which they live. Nor are they the only group that has used violence to try to gain independence.
The Kurds have long desired to set up a country they would call Kurdistan including land currently a part of Turkey, Iraq, Syria and Iran. If the U.N. grants membership to the Palestinians, shouldn't it also grant membership to Kurdistan? The Kurds have their own culture and language.
The Palestinians are a collection of Arab peoples who happen to live within the boundaries of the nation of Israel. They are called Palestinians not because they have a unique culture like the Kurds, but because they aren't Jewish. The term "Palestine" was used by the Romans to refer to a geographic region rather than any specific ethnic group.
Might the area of Chechnya also qualify for U.N. membership? What about the Basque region of Spain? Could Tibetans argue that they should have U.N. membership even though the Chinese currently occupy the country?
If the Palestinians should get their own country because they are Muslims, what about the Uighur Muslims in China?
Many other countries have groups that might want their own country if they thought it were possible, particularly in those areas of the world where European nations arbitrarily forced different ethnic groups to live in the same country. Granting U.N. membership to the Palestinians would encourage members of these groups to develop nationalist aspirations.
There is nothing special about the Palestinians. Many groups of people would like to have their own nations. The U.N. cannot arbitrarily grant membership to the Palestinians and ignore the aspirations of the Kurds, Basques, etc.
Nations that are considering voting for Palestinian membership should make sure they don't have groups that might make a similar request.
Over the last several thousand years regions of the Middle East have been controlled by whatever ethnic groups have been strongest at the time. Some groups such as the Persians and Assyrians have established empires. Others such as the Israelites have been content to control only small areas. The current situation in Israel has been occurred many times in the past and will likely to be repeated in one country or another in the future.
The U.N. should not attempt to arbitrarily adjust national boundaries or decide which groups should have their own countries. Many of the ethnic problems in Asia and Africa are due in part to the arbitrary national boundaries imposed by imperialistic European nations If the Palestinians, Kurds or other groups want their own nations they should handle their own situations rather having the U.N. impose a solution from outside.