The retort misses the whole point of the original essay. The essay was meant to be a tongue-in-cheek exploration of an oddity in our culture: that people who are asked to speak to esteemed crowds often express humility instead of what they really feel. Plus, the essay wasn't implying superiority, it was asserting it. After all, the speaker was asked to impart wisdom to the "overachieving straight-A students" at the ceremony. That implies a certain degree of superiority—the speaker is capable of imparting something that those students do not yet possess.
That being said, there is certainly an element of honor and privilege in being asked to speak to an esteemed crowd, and it would be wrong to imply otherwise. And while you may not feel humble in the traditional sense, you should still recognize that your presence is a privilege and be grateful for it. It's wrong to think that expressing humility diminishes your presence or devalues the invitation. In fact, if anything, expressing your thanks for being asked to speak turns your presence into something even more special for those in attendance.
In short, the essay didn't suggest a lack of gratitude or appreciation for the invitation; just the opposite. It's about recognizing the honor of the invitation and expressing true gratitude in a way that doesn't diminish it—and yes, with a cheeky touch of humor. So instead of focusing on how one should feel “humbled”, it's best to just recognize the good fortune of being asked to share wisdom with a unique group of individuals and have fun with it. After all, if everyone just dares to express themselves in their own unique way, boring commencement speeches would be a thing of the past!