The Spartan's visor slightly faces him as he mentions the use of killing as a solution. That was Spartan philosophy at its finest, right there, unbeknown to Kanda. Only guessing that there was an A.I. that could be eavesdropping, he would have agreed with the decision, as well.

"I know she's strong."

She was one of the strongest people he had ever met. A mind as sharp as Halsey's.

"But no one should ever fight alone."

As strong as one can be. He already knows what is it like.