That website is a Mohommedan one, but the Darwin quotes are still valid.
Note that Darwin refers in those quotes to the "civilized" versus the "savage" races of mankind. IOW he was focusing on the cultural as opposed to the biological differences. So this is primarily a rejection of cultural relativism, something a FReeper should have no problem with.
At worst Darwin, at least in these quotes, fails to envision the savage races becoming civilized, and instead anticipates them being "replaced". That perspective is pretty easy to excuse, however, if you remember some of the things Darwin had seen for himself or heard of at close remove during his voyage on The Beagle.
Darwin had been in Argentina, traveling cross country extensively on horseback, at a time when whites were waging an explicit war of extermination against the indians. Likewise Darwin visited Australia not long after the aboriginies there and been decimated, and the Tasmanian natives fully exterminated save for a literal handful of individuals (who themselves would expire with no issue).
BTW, the governor of Tasmania literally organized hunts of the natives, ordering the settlers into long skirmish lines to traverse the country side shooting aboriginies on sight. Of course this man knew nothing of Darwin's yet-to-be-formulated evolutionary views. Indeed he was a pious, passionate and conservative Christian.
Darwin never approved the extermination of native peoples. He considered this odious and immoral. He was simply extrapolating from facts on the ground.
Elsewhere in the Descent of Man, where Darwin does address biological issues of races specifically, we learned that he considers the biological differences between human races to be trivial.
The full text of The Descent of Man is available many places online, for instance here. Read chapter seven "ON THE RACES OF MAN" for Darwin's actual view on the biological significance of race.