people have always looked out for their own interests, and in the long run will not be convinced to vote against them.

Middle-class Americans have been voting against their own interests since at least 1980, when Reagan rode them into power and started shifting money from the middle class to the rich, which shifting has continued to this very day. It is not in the best interest of most Americans to deregulate industry or reduce the taxes of the super-rich. Capping the Social Security tax was against the best interests of the middle class, for instance, but did the middle class toss out the party that did it? Like hell.

It is what active Islamists have always done upon the conquest of an enemy.

Unfortunately for your point of view, the people wanting to build the mosque aren't active Islamists. But there are lots of interesting things to see under the sand.