Some people, by virtue of an aspect of their appearance may be prone to being treated like a second-class citizen. For example, a short person may as a result of their smaller size become aware that larger people tend to expect them to move aside so the larger person can pass. Another example is that a man may find that women expect he will hop aside for them to pass. As a result of being aware of these expectations that suggest they are the second-class citizen, when in fact they are not, these people may not surprisingly become aggressive. This aggressive behavior may become evident during any activity such as driving or cycling. As a consequence, you will also have the other person who is the bigger person or the person who feels favored in some way because of gender, color or upbringing - they will not take it well when the person they thought was a second-class citizen makes it known that they do not see themselves as second-class. So these self-proclaimed favored types will become aggressive when they a not treated as though they think they should be.
So, what we have is a whole lot of aggressive people, who are that way because some people are too stupid too realize that people should be treated fairly and shown reasonable courtesy no matter what or who they are.