This is a persistent myth that both some "nationalists" and liberals still keeps promoting despite historical evidence being against it.
The reason most Indian kingdoms didn't invade outside was geographic barriers and the lack of economic incentives not some moral superiority of pacifism.
Look at the borders of the subcontinent. To the west barren mountains of Hindu Kush, to the North, the mighty Himalayas, and beyond that barren plains of Tibet, to the east the Jungles of Burma and to the south thousands of miles of ocean.
And despite all of this, Indian kingdoms have invaded outside when there was an incentive
Splitting, or binary thinking, is a distortion where a person cannot integrate both positive and negative aspects into a balanced view, seeing things as all good or all bad. It appears in Cluster B disorders like borderline and narcissistic personality, and also in schizophrenia and depression.