CBS and NBC have refused to air a provocative ad from the confrontational, well-funded National Republican Trust PAC that calls on Americans to oppose the building of a mosque two blocks from the World Trade Center site. The ad — which has about 100,000 views on YouTube — intersperses some of the most horrifying images from the Sept. 11 attacks with the sounds of Muslim prayer and images of Muslim militants. It focuses on what's become a divisive — and partisan — issue in New York state, the erection of a Muslim cultural center on Park Place, in the neighborhood