When answering the question as to why supporting Palestine is not anti-Semitic it is important to bring attention to who the Palestinian people are, that is the native inhabitants of Palestine. Because the Palestinians are indigenous to Palestine this means that both their cultural and ethnic identity is tied to their connections to the land.
So, what exactly is happening in Palestine? To summarize, the Arab Jews, Arab Muslims and the Arab Christians have been living together somewhat peacefully for many years and these religions share many of the same historic landmarks and places of worship. When anti-Semitism grew in Europe at the height of World War Two, Palestine took in many Jewish refugees. As antisemitism grew so did the ideology of wanting a Jewish only state – also known as the Zionist movement. The real problem began when Britain gave away pieces of Palestinian land to the European Jews without consulting any of the surrounding Arab countries. There was temporary peace until the Zionists pushed for more; land was split again with the Zionists having access to the most resources. Soon, the majority of Palestinians were denied access to resources, homes were illegally occupied, and their movement restricted.
Here is a list of things Palestinians cannot do: they cannot leave or go back to their country, access transport or medical help nor even access clean water. They are constantly monitored, evacuated without warning from their homes and some are openly killed by Occupation Forces.
So, what does antisemitism mean? This is a form of discrimination or prejudice directed towards the individuals or groups that identify as Jewish. Now, what is Zionism in more context? It is a movement and an ideology that believes that Palestine belongs only to the Jewish people without taking the pre-existing Palestinian people into any consideration. This is leading to an ethnic cleanse of the Palestinian population with Jewish people being granted more rights. Israeli, Zionists, are the oppressors and Palestinians are the oppressed. Supporting Palestine is NOT antisemitism but rather anti-Zionism. Do not confuse the two.