BRESCIA, Italy, Aug. 23 — A series of unrelated killings here this month has pushed this elegant city to the center of a national debate on the challenges of immigration and cultural integration. The trigger was the gruesome killing on Aug. 11 of Hina Saleem, a 20-year-old woman whose family moved here from Pakistan and who was found buried, with her throat slit, in the garden of her family home in a small town about 12 miles north of Brescia. The tragedy ballooned into a cause célèbre after media reports alleged that Ms. Saleem had been killed because her traditionalist...