You are right, bitcon is supposed to be free, but now bitcoin is not completely decentralized, there are many big whales that may be controlling their prices, which is inevitable, but I believe there will be one day bitcoin Can really achieve decentralization.
It need people cooperation to be trully decentralized and human flaws like greed and lust for power will make it REALLY REALLY hard.
That aside, even whale have reasons to not use his power against bitcoin since its whale wealth also.