I would be upset if any body I knew gave up the one true living GOD of the Universe, The GOD of Abraham the GOD of the JEWS the GENTILES to embrace idolatry....
Well, now you know how Jews feel.
Jews who know their faith do not feel that there is a void in their religion. They are not waiting for you or other Christians to convert them away from Judaism. They are very comfortable with their faith. They believe that their faith is the true and correct one, just as you believe that yours is the same.
Unlike Christianity, Judaism takes a live-and-let-live point of view. Not only does it not try to convert non-Jews to Judaism, but it discourages those who want to convert to Judaism. (On the other hand, Judaism is actively involved in outreach to non-religious Jews.)
The only kind of outreach to Gentiles that Jews do -- and not very aggressively -- is to encourage them to become b'nai Noah, or to obey the seven Noahide laws that, to Jews, demarcate the difference between civilized and primitive peoples.
And I would be upset if anybody I knew gave up that God's only true Son, the Savior of the world.