I didn't say that he advocated extermination of inferior races. However, what he viewed as its inevitability didn't seem to bother him much either.
He saw it happening. The Europeans were exploring the world, and the savage tribes on isolated islands were rapidly dying off. Partly from disease, partly from poachers on their lands. Partly from who knows what. But it was happening worldwide, and it was quite visible. Yet there was no organized campaign of extermination, and least of all was anything like that advocated by Darwin. He was an observer. Stridently anti-slavery too.