If this is to be truly a multi-faith center, as the Imam claims, then this center should truly be a multi-faith center where every religion can worship as they please, and there can be ecumenical and inter-faith services there.
It should not be an Islamic center first and an inter-faith center second. The area where it is to be located is hallowed ground, where people from all faiths and all countries died. The center should honor all of these people. The USA is a country that honors the rights of all people to worship as they please. The proposed center should be a memorial to all faiths and all nationalities, not just Islam, or even an Islamic center that allows other religions to be represented there. Islam should be just one of the faiths that will be represented at the center. The center should be dedicated to all faiths and not favor one over the others.