When a Montclair bookstore canceled Jenan Matari’s book signing after complaints about her public statements on Israel, the Palestinian American author confessed she was not surprised. In a politically charged climate, pro-Palestinian and anti-Israel speech has often led to cancellations of speakers, art shows and books across the country. In New Jersey, Matari’s blunt criticism of Israel and Zionism sparked complaints to Watchung Booksellers, which pulled the plug on the Sept. 14 event. But instead of isolating her, the incident appeared to amplify Matari’s voice and her reach. As word of the cancellation spread, Jewish activists quicky organized to hold...