Is there a word which describes the tactic of labeling something you agree with "pro" and therefore implying the opposite point of view is "anti"? For example, pro-life, pro-choice, pro-transit vs anti-car, etc.
As choster's comment above indicates, one way of describing the practice of habitually expressing one's views as "pro X" (with the implication that anyone who disagrees with those views is "anti X") is to view it as creating a false dilemma, which is essentially an attempt to assume that a problem has only two possible (and opposite) solutions.
Another way to look at this tactic is to see it as an effort to frame the debate as being between one positive, creative, proactive side and one negative, destructive, reactionary side. Wikipedia has interesting articles on framing effect and on framing in general.
Of course it's not impossible that dividing the world of opinion in this way may sometimes be an accurate reflection of reality, but it usually isn't accurate at all. A single word that describes a person who acts as though it is always a valid approach might be dichotomist, which Merriam-Webster's Eleventh Collegiate Dictionary (2003) defines as follows:
dichotomist n (ca. 1592) one that dichotomizes [that is, "divides [things] into two parts, classes, or groups"]
The Eleventh Collegiate's definition of dichotomy notes that it consists of "a division into two esp[ecially] mutually exclusive or contradictory groups or entities." That sounds like what the person you describe wants to accomplish.