Mr. Kurtz "went native", and you saw what happened to him, right? In any encounter with the unknown or the unfamiliar, most people will insist on meeting it on their own terms -- what we in "civilized" countries like to call "civilized" terms -- rather than on its own terms. They usually call this "morality", for reasons they could probably explain better than I.
During the great age of European colonial expansion, explorers were followed by garrisons and accountants. What most of them had in common on their way out to the colonies was a firm belief in the superiority of their own culture and religion. After all, they had ships and guns, and they beat the hell out of most of the cultures they ran into. They were pleased with themselves.
They ran into trouble. The English Arctic expeditions, starting in the Ross and Parry voyage of 1818-19, set out dressed for England and provisioned for the South Seas. They met Eskimos and laughed at those silly people with their silly customs. The laughter sounded funny after their teeth fell out from scurvy, but they kept on laughing. They certainly didn't eat blubber, raw meat, and the contents of deer's stomachs. Maybe they would have if they'd understood the vitamin situation, but they didn't, and they didn't stop to wonder why the Eskimos weren't subject to the same deficiency diseases as they were. They didn't wear sealskins, and they were very cold. They didn't live like the natives: They lived like Englishmen, by God -- civilized people!
The same sort of thing happened all over the world: "Only mad dogs and Englishmen go out in the midday sun", as they say. They went to strange and wonderful places, but they thought it might be best to keep their distance. Of course, you can't really do that. Local words pervaded the Anglo-Indian vocabulary and the English in India learned to eat local food as well -- up to a point. Over time, the Raj started to look and feel more than a little bit Indian around the edges. You can spend a year in the Arctic without adapting, but you can't spend a lifetime anywhere without adapting at least a little bit. India is not England, and reality may at times intrude in small ways even on the English. Still, they wore English clothes, they married other English people, they stayed Christian and clove to English Christian mores, they still spoke English, and home was England. For the most part.
Some of them adapted more than just a little bit. The few who adopted the customs and outlook of the locals had "gone native". This was more common in less well-funded and "civilized" colonial operations: The French trappers in Canada often married local women, and the frontiersmen of the US didn't bring china with them. There's no sense of moral failing in that, really. They were practical people and they took life as it came. Heart of Darkness is a different matter: Kurtz's "going native" is a fall from grace, a terrifying and fundamental collapse. That's just a story, but myths tell us a lot about what people are thinking.
Myth is one thing, and reality is another. A great deal of money and power was at stake and there was a corresponding need for men who could adapt. Richard Francis Burton's xenophilia was worth a lot to the Empire: Not quite respectable, but valuable. T.E. Lawrence (you've seen Lawrence of Arabia, right?1) is another fine example. If I could find my copy of Seven Pillars of Wisdom, I might be able to quote accurately his remark about the joy of "breathing in great gusts of Orient" during his youthful travels in the Middle East, long before he did anything worth hiring Peter O'Toole to portray. Both of those guys walked a thin line. They never vanished into the desert or the jungle. Some did, but we don't often get to read much about those.
1I haven't seen it recently myself and you probably haven't seen it at all -- and there is nothing meaningful about it in the database as of this writing -- so I'll do a bit of a recap: The Arabian Peninsula was an issue during the First World War. T.E. Lawrence was a young English lieutenant who went out there and blew smoke up the Foreign Office's ass while organizing the local Bedouin to fight a guerilla war against the Turks, who were allied with Germany. He later wrote a memoir entitled Seven Pillars of Wisdom; he called it that because he just liked the sound of the title and wanted to use it. The strategic overview/Foreign Office bits of Seven Pillars have something of the flavor of the Egyptian portions of V2, except deadly boring. I never did get to the exciting part.
2If I have to tell you that Thomas Pynchon wrote that one, we have nothing further to discuss.