Final answer:
The speaker develops pathos by using evocative language that stirs fear and concern for the future of the society, emphasizing the need to maintain law and order to prevent the spread of 'cancerous' social decline.
Step-by-step explanation:
The speaker in the excerpt develops pathos primarily by using evocative language to invoke a sense of fear and concern about the future of the society. This is apparent through terms like 'cancerous growth of doubt, suspicion, fear, and hatred' which connect strongly to emotions that the audience may fear towards the destruction of social values and public order. Notably, the speaker argues against violence, anarchy, and the disintegration of law and order as justifications for social issues like poverty and discrimination. Instead, the speaker insists on maintaining law and order to protect the civil rights of all citizens. The emotional appeal is also fortified by alluding to a future where these ills 'infect the whole nation,' compounding the audience's concern for the welfare of society at large.