MANILA — Once, when Rodrigo Duterte got to talking about his anti-drug campaign, he mused about murdering his children. If his son used drugs, he said in April, he would kill him himself. 
 But seven months and some 7,000 deaths into his self-proclaimed “drug war,” the Philippine president’s children are alive and well. The same cannot be said for thousands of Filipino children and youths.
 Duterte’s war on drugs is quickly morphing into a campaign against disadvantaged kids. Since he came to power last July promising to “kill all” the country’s criminals, some of the Philippines’ youngest and most vulnerable citizens have literally been caught in the crossfire, with children as young as 4 and 5 shot dead.
 Thousands of others have lost a parent, often the family breadwinner, to the violence, and even more have witnessed the macabre spectacle of a state-backed killing spree, surviving shootings by hiding, or peering at …