The exchanges have so many currency in their cold storage they can indeed do nasty things to their "customers" and to the ecosystem of each cryptocurrency.
But the main thing that can drive them in that direction is something all humans have:
greed. Luckily that usually means "game over" for that business and keeping the business going may make them good enough amounts of money to not be inclined to do those nasty things.
The Illuminati are ... usually a good keyword to make people ignore your posts