I honestly don't know how Columbus should be taught in schools. He was one of the most pivotal figures of positive change in the last milenium. He was also a rapist. Not easy to distill into an 8th grade history lesson.
If Columbus had not sailed, the New World would have been discovered not long afterwards by the Portuguese or by the English, and the Portuguese voyages to India and East Asia would have begun to wake the Europeans up from their provincialism even if the New World had remained unknown.
Columbus spent most of his time in the New World unsuccessfully looking for a passage to India. He had little control over the colonists in Hispanola, whose natives were forced into labor because the Spanish were trying to make a profit on their expedition. This was the same thing that the Spanish had done in the Canaries earlier, but even this was sop in an era of war between the Spaniards and the Moors. Disease. of course, was the main killer, rape etc. being no worse than usual in wars of conquest.