He's writing from a certain time, place, and culture, in reference to the teas that were available to him at that time. I'm not sure what you're arguing - that black tea didn't subjectively make him feel wiser, braver or more optimistic? And his tips for making black tea are perfectly sound.

If I remember correctly, he actually wrote that essay because there was a world event that his compatriots were getting outraged about, and this was his way of being provocative by not covering it. But I may have that wrong.