Imagine yourself as the sociologist who wrote a theory.
You were called in to court to answer the charge that your new theory was contradicting accepted sociological principles. It is in this case that you would have to answer the charge "by pointing out that it did not in fact contradict accepted sociological principles"
Hence the blank should have a word that suggests something that is against accepted sociological beliefs and principles and therefore, "heretical" is the correct answer.
The part in the sentence after "that" tells you what the charge was and the part after "by pointing out" tells you how the sociologist responded to the charge.