Story highlights Charles Koch is one half of the political kingmaking brothers who have pledged $900 million to back Republican candidates this election cycle

Asked about Trump's proposal for a registry of Muslims in the U.S., Koch said, "Well, then you destroy a free society"

(CNN) GOP kingmaker Charles Koch said he is "disappointed" by the field of 2016 Republican candidates and sharply criticized the rhetoric and policies put forth by front-runners Donald Trump and Ted Cruz.

Koch, who along with billionaire brother David famously pledged to spend $900 million supporting Republicans in 2016, expressed dissatisfaction with the GOP primary thus far during a lengthy interview with the Financial Times published Friday.

Asked about Trump's proposal for a registry of Muslims in the U.S., Koch said, "Well, then you destroy a free society ... Who is it that said, 'If you want to defend your liberty, the first thing you've got to do is defend the liberty of people you like the least?'"

Koch also panned Cruz's aggressive strategy to fight ISIS, which has included calls for "carpet bombing" and declarations that Cruz would direct strikes until "sand glows in the dark."

"I've studied revolutionaries a lot," Koch said. "Mao said that the people are the sea in which the revolutionary swims. Not that we don't need to defend ourselves and have better intelligence and all that, but how do we create an unfriendly sea for the terrorists in the Muslims communities? We haven't done a good job of that."

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