A Passage to India - Colonialism. Why are we here?

Like many explorations of colonisation there is always a fundamental difficulty that no matter how deeply investigated and logically reasoned fails to be fully addressed; the coloniser despite just and reasonable justifications has no choice but to trail off into silence or obscurity. Marlowe in Conrad's 'Heart of Darkness' is just as guilty of this as Ronny here arguing with his perhaps naive mother who maybe comes as close to the issue as possible:

''We're not out here for the purpose of behaving pleasantly!'
'What do you mean?'
'...We're out here to do justice and keep the peace. Them's my sentiments. India isn't a drawing room.'
'Your sentiments are those of a god,' she said quietly...
...'India likes gods.'
'And Englishmen like posing as gods.'
'There's no point in all of this...I am out here to work, mind, to hold this wretched country by force. I'm not a missionary or a Labour Member or a vague sentimental sympathetic literary man. I'm just a servant of the Government...We're not pleasant in India, and we don't intend to be pleasant. We've something more important to do.'
   He spoke sincerely. Every day he worked hard in the court trying to decide which of two untrue accounts was the less untrue, trying to dispense justice fearlessly, to protect the weak against the less weak, the incoherent against the plausible, surrounded by lies and flattery. That morning he had convicted a railway clerk of overcharging pilgrims for their tickets, and a Pathan of attempted rape. He expected no gratitude, no recognition for this, and both clerk and Pathan might appeal, bribe their witnesses more effectually in the interval, and get their sentences reversed.
...He spoke sincerely, but she could have wished with less gusto. How Ronny revelled in the drawbacks of his situation! how he did rub it in that he was not in India to behave pleasantly, and derived positive satisfaction therefrom!'
...'I'm going to argue, and indeed dictate, ' she said...'The English are out here to be pleasant.'
'How do you make that out, mother?' he asked, speaking gently again, for he was ashamed of his irritability.
'Because India is part of the earth. And God has put us on the earth in order to be pleasant to each other. God...is...love.' She hesitated, seeing how much he disliked the argument, but something made her go on. 'God has put us on earth to love our neighbours and to show it, and He is omnipresent, even in India, to see how we are succeeding...The desire to behave pleasantly satisfies God...The sincere if impotent desire wins His blessing. I think everyone fails, but there are so many kinds of failure. Goodwill and more goodwill and more goodwill.'' -pp.69-71