Colonialism is a fancy word for armed robbery. It’s not trade if it’s done at the end of a barrel. The Indians could have easily grown and then manufactured their own cotton and kept the proceeds, if it was just about “trade”. Furthermore, much of that “trade” came about from the proceeds of slave labor on land that had been stolen. The important words in all of this are - theft, stolen, force and violence. That doesn’t sound much like trade to me.
And yes, empire and mass population movements do tend to be related. Creating instability and then taking credit for quelling the disquiet that they caused or blaming some third agencies for the anarchy caused by the empire is what empires tend to do.
Tell the Brits to suck it up. They made their flea ridden bed and now it’s time to take a nap in it.