"The only reason we (NATO) has not crushed them is because of humanitarian reasons, we feel bad for their people being enslaved and fear that engaging in war would starve their people and send their already weak army into a war they are not equipped to fight."
There's also the fact that if we actually militarily threatened them there'd be thousands of missiles fired, and Seoul would be ashes. There's also a risk that they could use nuclear weapons or chemical weapons on S. Korea. N. Korea is a state that has sacrificed everything to prop up a military regime, and invests more in its military than any other part of society. S. Korea with the US as an ally would certainly win a conflict, but N. Korea could cause some seriously devastating carnage before it was over.