Yes, the ad was stupid, by why is it offensive to American Jews. It's a fact that over 50% of American Jews, especially non-orthodox, intermarry and the second and third generations totally lose connection with the Jewish Community. The threat is real and there's nothing offensive about pointing it out.
Pakistan: Suicide bomber attacks tribal police, killing 4 (Reuters)
from the article: Why Israel's expat campaign offended so many U.S. Jews