Why? It's just another part of a pattern of nasty eliminationist rhetoric from Coulter. She likes to talk about killing people who don't agree with her ideology.
I think She was venting anger at an Ideology, that has in part declared a Jihad against Western Culture, 2 days after the worst Domestic Attack on record of our Natures History.
One thing She cannot be accused of is refusing to acknowledge the Threat against Us, by Jihad, and even Sharia.
Personally I have no issue with Anyone with the words they use when they Pray, that is between Each Individual and Their Maker, Hopefully involving Conscience. Killing People, Imprisoning them, Enslaving them, because they refuse to conform to your will, is another matter.