The simple, easy, and cynical answer to the question is, "Yes, of course. People are ridiculous, pitiful,and silly." Perhaps a better response though is the fuzzy, non-committal "yes and no." Let's consider another, similar question: Are dogs stupid? Well, of course dogs are stupid. But dogs are just dogs; why would we expect more of them? Maybe the problem in considering man is our expectations. There are two angles from which to consider whether homo sapiens are stupid creatures; our expectations color our understanding.
A positive perspective of man would defend the mental powers of homo sapiens. We can see how far above the animal kingdom man is--reasoning, self-awareness, power of speech. Our brains are such complex machines: the pinnacle of nature's wonders! We form technologies, we create through the arts, develop societies, and civilize our world; no other animal than the human animal sets about the environment in such a way.
Now the folly of man is a much more interesting perspective to take. The tomes of anthropology cannot account for man's misadventures. Wars, economic disasters, fallen civilizations, et al. scream out the inherent buffoonery of the homo sapien. Pull back to observe the quotidian, then marvel at the absurdity of it. Life is full of mis-steps and poor decision to bring despair to the most ardent of humanists. In many ways, we are not that much further up the natural order from the animals. Our primal urges to feed, mate, and survive have little to do with reason and more to do with survival.
Objectivity eludes us, we are trapped inside our subjectivity, limited to our own perspective, and never fully understand other viewpoints--we are masters at deceiving ourselves!