Answer:
C. challenging established ideas
Step-by-step explanation:
The established idea the speaker is challenging is the issue concerned with a liberal immigration policy. This idea, in the speaker's view, is being supported by an author who is trying to emmigrate himself to America. Therefore ,there is no point in discussing about a policy to allow free immigration if this idea will be supported by an author directly affected by the situation. The speaker puts it in these words: "..to consider the issue fairly."