Most conservative libertarians these days are ex-neocons, they could accept statements like '"We're overextended and these wars achieve less than hoped for" but they are not receptive to "We are in the wrong, period" and his various other points only appeal inside the core party to the conservative libertarians. His stance on drugs is even a bit much for 'conservative libertarians' who generally are of the 'Pot? I suppose so, tax it and regulate it, maybe some other stuff' not full blown purchase of Cocaine at Walmart. So the group - in the mainstream conservative movement and the GOP - most likely to support him is pretty much turned off by his attitudes on defense.