This is an old stuff, I have read a hundred times and sick of reading it over and over again. Every author just keeps saying whatever nonsense it is that comes to their mind just to gain whatever it is they plan for. Yes we know that Bitcoin is volatile because of people invest a lot of money and withdraws when they have made huge profits. Well, its a normal thing in this business and can also be found in most business out there.
Bitcoin is volatile, and being volatile is what helps most of us make profit. Those who are quick and smart will always invest at the right and also withdraw when its right to avoid losing their money. There are always people manipulating the price. Its left for you to play the game smart, if you can.