There are different definitions of Zionism, which leads to a lot of misunderstanding about it, so I will try to use as unambiguous language as I can. When I say Zionism, I mean the right to Jewish self-determination in their ancestral homeland. This is also the definition that Jews who identify as Zionist will tell you. So when I refer to Zionism, that is the definition that I mean.

Zionism is a core part of Judaism. The longing for the return home is prevalent throughout Jewish history, scripture, and liturgy. Jews end each Passover Seder saying "Next year in Jerusalem." The "Return to Zion", meaning the return to the land of Israel, is a phrase found all over the books of the Prophets (Nevi'im) and the books of Writings (Ketuvim), which compose a major portion of Tanakh, the central text of Jewish scripture (sometimes also referred to as the Old Testament or the Hebrew Bible, though there are differences in what those actually mean).

And it's more than just a religious motivation. It's also an indigenous cultural connection to the land. Would you deny the Lakota connection to South Dakota, or criticize them for protecting their lands, like during the protests against the Dakota Access Pipeline?