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Their spin is "the IRS are big meanies who audit regular people so we should get rid of them." They're hoping that their base shouts "yay! No more taxes!" despite this having zero chance of passing. 
Of course, if it passed, it would be replaced by something akin to a national sales tax which would impact the poor/middle class much more than the wealthy. Either that, or they'd say "the government has no more income so it's time to cut everything!"
Of course they did. The wealthy corporations and donors can't have the pesky IRS discovering their tax cheating. Real patriots.