As background, the first natives Columbus met were helpful, peaceful Arawaks. Columbus, without any apparent moral qualms, captured some of them and used them as guides, interpreters and intended to bring them back to Spain to show to the King and Queen. His actions seemed natural and unquestioned as there is no record of debate on the topic.
While the Arawaks were peaceful, the neighboring Caribs were not. They were slavers and cannibals and the Arawaks were terrified of them.
Columbus and the Spaniards are frequently portrayed as greedy thieves and racist maniacs. Whatever their motives, let's engage in a little alternate history fantasy for a moment. Imagine that the Arawaks, instead of possessing technology equivalent to the Caribs, had superior weapons and boats? Now assume that this technological disparity lasted for, say, 200 years. Don't you think that over a 200 year time period, even the peaceful Arawaks would eventually say to each other, "You know, I've had my fill of these little swine Caribs. They can't seem to control themselves. Let's go finish them off once and for all."
Or how about this: "My wife and kids never seem to have enough fish to eat. Those pathetic Caribs do nothing but use up resources and make trouble. Let's go beat the tar out of them and take their islands."
There's an offhand remark in the book that some of the native tribes had done just that prior to Columbus' arrival, blotting out some particularly annoying neighbors. The Aztecs most certainly did that to bordering tribes prior to Cortez.
So what's the big deal with singling out the Spaniards? Yep, they killed to looted. Columbus himself was monomaniacal about finding gold. I find it hard to believe that any of their contemporaries would have acted differently.
Here, we see Arawak battleships in action against the Caribs.