Tomas van Houtryve for The New York Times Jean-François Bastin, 61, a Belgian convert to Islam, in his home in Brussels. His party is aggressively pursuing a pro-Muslim agenda. ANTWERP, Belgium - Filip Dewinter, a boyish man in a dark blue suit, bounds up two flights of steep stairs in his political party's 19th-century headquarters building where posters show a Muslim minaret rising menacingly above the Gothic steeple of the city's cathedral. "The radical Muslims are organizing themselves in Europe," he declared. "Other political parties, they are very worried about the Muslim votes and say let's be tolerant, while...