Two major events in the course of Indian history were mostly responsible in developing general British psyche about Indians or rather the Asiatics. The first event would be the consolidation of British rule in India after Pitt's India act in the late 18th Century, a time when the trade balance has already been shifted massively towards Britain. India was no longer a rich country but a region of million impoverished, incapable of governing themselves and spiritually motivated by ancient faiths filled with superstitions and countless horrifying rituals. A sense of racial and moral superiority over the Asiatics was born already though Edmund Burke was relentlessly preaching against the unethical and corrupt British colonialism ( in his four days impeachment against Warren Hastings to be precise) which put millions to death in the notorious Bengal famine in 1770.
The regular social intercourse between West and East came to halt after 1857. Although England came with India bill in 1858 which meant to provide the Indians more sovereignty in terms of governing themselves, British could not trust Indians any more. Winston Churchill is a perfect product of this generation when British aristocracy was vastly inspired by a sense of isolationism from the Asiatic inferiors who were not only racially belong to a inferior branch but also politically and spiritually impotent to elevate themselves ever to the European standard. But it must be considered that, Europe at the same period was going through an intellectual revolution. Prominent thinkers like Adam Smith, Edmund Burke, The Mills or Marx came with ideas of liberalism and socialism which were never heard of before; later which would influence extra ordinarily the radical opposition of colonialism in India and West Asia. So it will be incorrect to paint the entire British in the same color of imperial racial superiority complex.