I cannot argue with his goal:
At this crucial time for Jews throughout the world, the Orthodox Union proclaims loud and clear that Jerusalem must be off the table. Any peace negotiations must be predicated upon the fact that Jerusalem will remain Israel’s undivided capital. We pray for it, yearn for it, fast because of its destruction, and remember it at our most joyous times under the chupah.And the article makes it clear that the entire purpose of moving the embassy is to be a part of a declaration by the US that Jerusalem is Israel's undivided capital.
Last night, I heard Israel's former Chief Rabbi Yisrael Meir Lau speak. He mentioned that in 1987 he spoke with a high-ranking US official, who told him that the reason that the United States didn't bother bringing up the question of Jerusalem because everyone knew that the Knesset was against dividing Jerusalem by roughly 116-4 seats. Against such a consensus, the US wouldn't bother wasting its time to pressure Israel to make concessions.
However, if there is a cleavage in Israeli society, the US will be happy to use leverage to exact concessions from the state.
Rabbi Lau went on to say that in the wake of the Mumbai attacks, all Israelis - religious or not - stood together as one. The unity is there in the face of terror, but not so much at any other time lately. And it is this lack of unity that gives the world a toehold into trying to shrink Israel.
The US is not going to be more Zionist than Israel itself is. The most left-wing Israeli governments will continue to move their "red lines" back while negotiating away Israel's strategic interests, and as soon as something new is on the table, it is difficult to remove it.
In this environment, if American Zionists insist on making the embassy a slogan, it is entirely conceivable that a US administration will say that they will be happy to move the embassy to western Jerusalem but insist that Jerusalem be divided as part of the deal. Emphasizing the embassy - a purely symbolic gesture - could end up facilitating the loss of much of Jerusalem on the ground.
The embassy is not the issue. Jerusalem as a unified capital of the Jewish state is the real issue. This is far more important than the symbolism - and likely resultant pressure - that would accompany any US move of its embassy.