In no way did Mr. Kristof justify terrorism, as you plainly say. Nor did Mr. Kristof say that Islamic terrorism is OK. You said that. In fact, Mr. Kristof didn't even say that guns are bad, you said that; nor did he say guns are "OK for Islamic terrorists to use ." Again, those are your words.

What Mr. Kristof did was to put the threat of Islamic terrorism into perspective among all the other threats we face in the US, and it turns out that Islamic terrorism is a minor threat indeed, compared to what US citizens themselves do to each other.