Exchanges whether centralized or decentralized can affect the price movement of any cryptocurrency, however this all depends a lot on how big is the influence of the exchange in the total marketplace. Small exchanges with low volume may not be making any dent at all. OKEx is certainly one of the top 10 big exchanges we have (I hope I got the raking right) so it has a pervasive influence which eventually resulted into a little decrease of Bitcoin price. Eventually, whatever can happen to OKEx will be balanced by other existing exchanges, there can just be a transfer of business but for the meantime we can all feel the impact. The story of MtGox illustrated how an exchange can change things and stop a market's momentum.