I didn't say start, I said run. The dilemma he speaks of (yes I have read the book) sounds good on paper but doesn't play out in the real world, there are plenty of examples, is Coca Cola afraid of launching a new soft drink, or does Tricorn worry KFC is eroding the market of Taco Bell? Like most economics or sociology it's an elegant model that has little basis in reality.
Go read it again. I don't think you're grasping the idea of disruption as Christensen defines it. The examples you give are not disruptive products - they're just new products.