What words does the author use to express Marlow's contempt for men?

Here is a quote that might suffice from part 2,

"Trees, trees, millions of trees, massive, immense, running up high; and at their foot, hugging the bank against the stream, crept the little begrimed steamboat, like a sluggish beetle crawling on the floor of a lofty portico. It made you feel very small, very lost, and yet it was not altogether depressing, that feeling. After all, if you were small, the grimy beetle crawled on – which was just what you wanted it to do." (2.7)

When set against this backdrop of immense wilderness, man seems very small indeed, as small as a "beetle crawling on the floor of a lofty portico." Though it would be understandable for Marlow to feel overwhelmed by his smallness, he twists his situation rather optimistically, saying that while a beetle is small, it still crawls towards its destination.