Smart people don't think others are stupid
There are no smart people or stupid people, just people being smart or being stupid.The same could be said about almost all behaviors, such as courage, promiscuity, or whathaveyou. However, over time people tend to display consistent patterns of behavior. As a consistent picture emerges, we tend to switch from thinking of people as acting a certain way, to thinking of people as being a certain way. Whether you want to say someone is acting stupid all the time, or someone is being stupid is just semantics.