Hello,
I heard that there is a whale that moved 8k BTC to an exchange and that what caused the price to go down in addition of Stop-Losses being triggered.Is that true?What do you think? If it's true I consider it to be a big problem as we clearly see that whales manipulate the market easily which is harmful.
I think OP is referring to this news:
https://www.ccn.com/mysterious-asian-whale-begins-funneling-funds-back-to-huobi/I wouldn't say that a whale moving coins around instantly means that the market is somehow being manipulated. Of course, the market could be manipulated by a variety of factors, but this isn't something that can be used as proof of "manipulation". Selling coins that is rightfully yours is something that can be done freely, doesn't matter if you have 8k BTC.
It shouldn't be taken as a sign of anything, really. It could literally be someone needing money to invest in other ventures, or that he feels like that bitcoin is going to go lower, so he's selling now.
It could be the reason why prices are down so much right now, but I feel like a lot of it is actually done by panic sellers themselves. I don't think there is any point in trying to monitor whale addresses, it's not a foolproof way to predict how bitcoin will move at all.