Some random musings... I think there's a sense in which we can legitimately say that Columbus "discovered" America -- in the same way that a young reader can "discover" the Tolkien trilogy. You can discover something very well-known and long-established indeed, if you yourself are ignorant of its existence until that moment. I have had that moment of "discovery" many times, stumbling across obscure (to me) books or movies.
The word "discover" is not necessarily the wrong word....
But I agree heartily with the author in that "discover" has a very particular and sinister meaning in Anglocentric colonial talk. It means "find something valuable and claim it for your own use and profit _as if no one else knew_ it was there." When Anglocentric legend says Columbus discovered America, they mean it in the sense that the burglar who was in your home discovered your cash stash hidden behind the microwave.
Terry Pratchett in one of his many fine Discworld novels introduced the idea that the Eurosphere's many Explorers' Clubs should be renamed Trespassers' Clubs, and this I think is a salutary correction. The problem with the traditional use of "explore" -- like "discover" -- is that it does indeed erase the existence of all the people who knew a territory long before the European "explorer" arrived. When areas are labelled "Terra Incognita" it means only that the map-maker was ignorant of them. They may be very cognita indeed -- to people already living there or migrating through with the seasons.
But rather than reflecting on their own _ignorance_ of the world, like the young person who never knew about Tolkien's works, the Eurocentric speaker pontificating about Exploration and Discovery -- in a moment of mental legerdemain -- erases instead everyone else's _knowledge_ of the world... so that tracts of land are described as "wilderness" that are actually inhabited, and Palestine for example is described as "a land without a people."
It's not so much the word "discover" that's at fault... it's how we use it and what's missing. Columbus discovered America, because he was _ignorant_ of it and had never been there before, like a tourist "discovering" San Francisco. But then he murdered its inhabitants and stole their wealth. So he belongs not just to the Trespassers' Club, but to the Homicidal Maniac Burglars' Club.