Washington (CNN) – The top U.S. commander for the fight against ISIS on Monday slammed the idea of “carpet bombing” the terror group.

Army Lt. Gen. Sean MacFarland, who directs the coalition fighting ISIS in Iraq and Syria, provided the most detailed military criticism to date about the concept and detailed why it’s militarily unacceptable.

“Indiscriminate bombing where we don’t care if we are killing innocents or combatants is just inconsistent with our values,” he said in response to a question from CNN on the possibility of using carpet bombing.

Though MacFarland didn’t mention any political candidates by name in his answer, Republican Sen. Ted Cruz of Texas while on the campaign trail has called for employing the practice against ISIS.

“We are the United States of America, and you know we have a set of guiding principles and those affect the way we, as professional soldiers, airmen, sailors marines conduct ourselves on the battlefield,” MacFarland said at a news conference from his Baghdad headquarters held before the Iowa caucuses. “We are bound by the laws of armed conflict. And you know at the end of the day, it doesn’t only matter if you win, it matters how you win.”

MacFarland noted that the Russians have been accused of indiscriminate bombing, killing large numbers of civilians in northwest Syria.

“Right now we have the moral high ground and I think that’s where we need to stay,” he said.

The notion of defeating ISIS by massive imprecise bombing in Iraq and Syria has been brought up several times during the Republican presidential race, with Cruz a particular advocate for the approach.