Malcolm X is saying something subtly different than "criticism means you're doing something important"—he's pointing out that the absence of critics is itself a warning sign, a kind of invisibility. When no one bothers to argue with you, it often means you haven't threatened the status quo enough to provoke a response. A small-town business owner told me she knew her shop had finally mattered when a competitor started publicly attacking her methods; the silence before that had been the real danger. Success, in his view, requires enough visibility and impact to draw opposition—which is why the most ambitious people should worry less about being liked and more about being noticed and contested.