Final answer:
Option B, which mentions that pioneers displaced and killed Native Americans to take their land, is the main point of the letter to the editor.
Step-by-step explanation:
The main point of the letter to the editor is option (B), which states that pioneers displaced and killed Native Americans in order to take their land. This theme is drawn from the historical context provided, which discusses the violent interactions between American settlers and Native American tribes during westward expansion. Settlers, supported by military forces and government policies like the Indian Removal Act, systematically removed Native American populations from their ancestral lands. The provided context highlights the inherent systemic and cultural disregard for Indigenous peoples, encapsulated in policies and actions during the era of Manifest Destiny.