Lot of things really impact bitcoin price and i agree with you that exchange website are the reason for the price drops. The sudden drop of bitcoin prices now is because no one buys bitcoin for a huge amount. All they want is to buy in low amount.
If you mean to say that buying low amounts of bitcoin makes the price drop then you are grossly mistaken. Whatever price or whatever amount they are bought at, will raise the price of the coin. It does not necessarily mean that every small buy order will move the market a lot but they have an effect cumulatively as people maintain a buying pressure. Seems like you have no idea how markets work and how trading bots pump and dump the prices.
Also I would not blame people for buying low amounts. One whole bitcoin is expensive for anybody coming newly into the market for whatever base currency rate we talk about.