Morse held strong nativist views, expressing concerns about the influence of immigrants, particularly Catholics, on American society. He wrote extensively on this topic, reflecting the anti-immigrant sentiment prevalent at the time.

Morse wrote a series of letters under the pseudonym 'Brutus' in the "New York Observer", expressing his anti-Catholic sentiments and warning against the perceived threat of Catholic immigration to American institutions and values.

Morse was involved in political organizations that promoted nativist agendas. His views, while controversial, reflected the anxieties of some Americans about rapid immigration and cultural change. He ran for Mayor of New York under the Native American Party banner, but lost.