That same "pure" form of capitalism
exists any time the established political system implicitly requires it; the requirement will never be explicit. Whenever the established system tends to strongly favor one group, while denying its benefits to others or when a commodity (e.g. drugs & alcohol) is too strongly regulated or denied by by that system, this "pure" capitalism springs up to make available that which is denied. Thus, "pure" capitalism existed in the USSR under the Soviet regime. It existed under Prohibition. It exists now under drug prohibition.
The problem with "pure" capitalism is it tends toward monopoly, and the potential/current monopolist will do what is necessary to gain or keep the monopoly. As this type of capitalism operates outside the established society, what is necessary is not usually restrained by current social mores. Thus, the gang wars and violence of the 20s were a natural process under "pure" capitalism...and the gang wars and violence of the last three decades are also a natural process.
