Philippine President Rodrigo Duterte’s frustration with Maoist terrorists in his country is understandable. When he extends an olive branch, they take bloody advantage of it. Just last week, as peace talks were going on between his government and the rebels, they attacked his presidential guard, wounding five of its members.

And, as so often is the case with both Islamic and communist terrorists, the Filipino rebels are fond of using civilians as human shields.

None of that excuses intentional targeting of civilians by Duterte’s troops.

Duterte’s tactics against the Maoist rebels have been criticized frequently. He has taken a hard-line, brutal approach to stamping out terrorism.

But a threat he made this week cannot be allowed to stand without some response — quietly, through diplomatic channels, if that seems best — from the United States.

Noting some schools, referred to as Lumads, are being used to intdoctrinate children in Maoist ideology, Duterte threatened to have his air force bomb them.

That is simply unacceptable. Should the schools be shut down? Possibly. Should rebels running them be arrested? Again, possibly.

Should children be killed because adults are trying to brainwash them? Under no circumstances.

Chances are Duterte was just blowing off steam. Again, that is understandable. But President Donald Trump’s administration should make it clear that intentionally targeting children with bombs would result in elimination of U.S. aid to Duterte’s regime.