They either say it's faulty but the best of the systems available, or just don't understand it generally. This is unfortunately because many capitalists are educated not on that Adam Smith (who I'll admit I only heard about recently), but on Ayn Rand (who really does flout it as perfection).
That's not exactly a groundbreaking concept, considering Adam Smith acknowledged it in The Wealth of the Nations, though it makes me wonder why so many capitalists today hold capitalism on a pedestal of perfection when even its founders outlined both its benefits and its detriments.