Power can be abused. I know a person who keeps saying "Bitcoin was created by the Government, we cannot trust it!" I point out we do not know that for certain, but am concerned about the huge amounts in old blocks that have not moved yet.
The circulating supply of Bitcoin is more than 19M already, so there isn't a large percentage of the coins left that are either lost or kept in wallets and haven't been moved since, so I don't see that amount being that big of a threat to its price even if the theory you and that person has turns out to be true which I doubt.
We know that financial markets are usually manipulated if a single entity acquires a large percentage of an asset, but that isn't easy when it comes to Bitcoin. Whales do manipulate the price to some extent, but it's only changes made that allow them to gain some profit and nothing threatening for the market or the majority of holders.
Thus, that theory doesn't sound realistic to me at all.