Of course manipulation by whales is happening and it is always "possible", but at the same time is it really that much possible for someone to pump and dump bitcoin? Unless they have tens of billions of dollars (Elon) then I am sure that not that many people would care. Look at Warren Buffet, dude is one of the richest in the world and he says he doesn't like bitcoin and the price doesn't change because of that, why would it change because of anything else?
I am guessing that people could do it with low level coins, the stuff that has very low volume and liquidity, but that is about it. They can do that with stocks too, go ahead and buy some pink slips and you could increase the price of it by a big margin.
I still believe whales can manipulate bitcoin, the market is very vulnerable just one big FUD is enough to manipulate the market let alone use money to manipulate. They can't manipulate for too long but enough to make a profit for them, Elon just tweeted that Tesla accepted bitcoin and the market reacted very quickly and when he announced that they don't support bitcoin it immediately dropped.
The stock market still has manipulation but not as much as cryptocurrencies, simply because it is regulated by the authorities, if any manipulation is detected, they should be caught immediately and held accountable, unlike cryptocurrencies, we are free here.