You are correct that the Magen David or shield of David was not originally a Jewish symbol. It is found in ancient art, both Jewish and non-Jewish, and it does not seem to have had a particularly Jewish meaning. Only in the last two hundred years, approximately, did it begin to be used as a Jewish symbol. Synagogues featured the symbol on the ark, on the velvet covering on the Torah, and on the Torah reading platform. It was used for Jewish coffins and gravestones.

When the Zionists searched for a symbol of their movement, they picked both the Magen David and the menorah: one for their flag, and one for their national seal. Since the Jewish people does not have much of an historical attachment to the Magen David, the Zionist appropriation of this symbol does not upset us too much. More upsetting is their use of the name Israel, the authentic name of the Jewish people, and the seven-branched menorah, which was commanded by G-d and stood in the Holy Temple for more than 1300 years.

The menorah is particularly inappropriate for the Zionists in view of the verses in the book of Zachariah (4:6), which Jews read aloud in the synagogue on Chanukah. Zachariah was shown a prophetic vision of a menorah. He asked an angel what the vision meant, and the angel replied, "This is the word of G-d to Zerubavel, saying: Not by might, and not by power, but by My spirit, said G-d of Hosts." Thus the menorah is a reminder that the Jews' redemption from exile will come in a miraculous way, not through human effort. How bitterly ironic is it, then, that the Zionist movement, which advocates the conquest of Eretz Yisroel by force of arms, has adopted the menorah as one of its national symbols!