In any discourse of the human condition, generalizations are made. We generalize demographics of the human populace as a simplifying tool with which we handle sweeping concepts or descriptors. We refer to groups such as "The Religious", "Atheists", "Liberals", "Republicans", "Christians", "Jews", "Muslims", "Children", "Adults" and other broad descriptors that help us to clarify the targets of our statements of discourse. This categorization helps us to identify the topic of our discourse, and also work to contextualize the conversations we have within our discourse.
When we interact with each other, we do so through conversation and discourse. In any media, there is a conversation - between the message that the media is presenting to its audience, and the reactions, emotional responses and cultural associative myths of the members of that audience. When we converse face to face, we experience the same thing. One person says something, and based on their emotional responses, reactions, and cultural associative myths of their co-conversationist, a reactive response is generated.
Granted these emotional reactive responses can be a commonplace affair. The statement "Vanilla Ice Cream is awful." will generate different responses in different people. Some will agree and may experience a feeling of increased compatibility or empathy with the speaker of that statement. Some will disagree, and may experience a feeling of reduction of compatibility or reduced empathy with the speaker. Some may find the statement irrelevant to their opinion or non-impactful if they have never experienced Vanilla Ice Cream, and then they may experience an information crux. Will they seek first hand knowledge of Vanilla Ice Cream, or will they accept the statement that "Vanilla Ice Cream is awful." and add it to their pool of cultural associative myths?
In some cases the emotional reactive responses can be more moving or life changing. Statements about groups of people can function in this way. If a person says "Red Heads have hotter tempers.” this can generate a distinct emotive response in people. For Red Headed people it can signify an attack against them as a demographic whole - thus placing them in a defensive frame of mind for the remainder of any conversation of discourse with the person making the statement. For non-Red Headed people it can act as a catalyst for judgment of Red Headed people. Those of us who do not have red hair, can agree or disagree with this stereotypical statement, and indeed red heads also have the freedom to agree or disagree with this statement. However, agreeance or disagreeance does not change the fact that the statement is a definitive stereotype of a particular, distinct demographic of humanity.
Yet, when we have discourse about humanity, our language is full of these stereotyping statements that function as descriptors and as attempts to categorize demographics to which our discourse is relevant. Statements of classification or stereotype group like minded or similarly featured people together into a single generic classification of being. Any statement or question that uses a term like "The Religious", "Atheists", "Liberals", "Republicans", "Christians", "Jews", "Muslims", "Children", "Adults" and any other broad descriptors that act as a system of classification or stereotyping in our language experience a danger of being viewed as an attack against a subset of people. "Red Heads have hotter tempers" functions as an attack against red heads. "Republicans have hotter tempers" functions as an attack against any people who may be, or consider themselves to be, or are sympathetic to those who claim to be republican.
When our social discourse includes these descriptive labels, we can observe a subsidiary symptom of the labeling process described by Dawkins in our opening quotation. Some people will take on the trappings of a projected label and "catch" the figurative bullet that they perceived aimed at "red heads" and/or "republicans". Why do they do this? Why do people assume the identity of a demographic they perceive as on the receiving end of a verbal or literary attack, and then proceed to take personal umbrage and behave defensively about a verbal sling that was not, in origin, aimed in their direction?