It's not on the World Trade Center grounds. It's planned for an adjacent neighborhood that already has two mosques. "Ground Zero Mosque" is just a bunch of demagoguery and jingoism.

The World Trade Center is a symbol of the dangers of religious extremism. While I would totally get behind a movement to deny any religious institutions access to the site, I don't think that would fly. Religious groups using their own funds and building their own monuments and cross-cultural institutions against extremism is as good as we're going to get.