What do you mean Ripple Labs sets the XRP price?
Exactly what it says.
As it is a centralized company they have full control of the price. If they want the price to go up they simple dont dump for a day. Unlike Bitcoin where a set number of coins is mined a day and noone can say no new coins today.
Ripple has only one indention to know when, where, what cola you drank, where you have spent some money, when you farded, what you eat, what you earn, basically you end up being a marionette.
What does being a centralized company have to do with price control in this situation? I'm not a centralized company but I can dump my holding and bring down the price too. There are a set number of XRP (100 billiion).