Final answer:
No conclusive evidence supports the claim that Native Americans were inherently hostile; conflicts arose mainly due to settlers encroaching on Native lands and breaking treaties.
Step-by-step explanation:
No, there is not enough evidence presented to support the argument that the Indians were hostile and a threat to immigration into the region. While it is mentioned that the U.S. Army sometimes dealt with acts of Indian retaliation and there were fears among settlers, it is also stated that many of these encounters were characterized by settler brutality.
Moreover, the overarching theme suggests that conflicts arose as American settlers encroached upon lands traditionally inhabited by the Native Americans, disrupting their way of life and breaking treaties like the First Treaty of Fort Laramie.
The resulting Plains Wars and other conflicts were often the consequence of aggressive expansionist policies rather than unprovoked hostility from Native American tribes.