There were several arguments that were made for going to war with Great Britain in 1812. First there were those who hoped to gain new territory from a war with Britain. They felt the U.S. could acquire Canada, and its lucrative fur trade, through a war with Britain. In addition, some hoped to gain Spanish Florida in a war with Britain because Spain was allied with Britain.
Another argument for war was the impressment of American sailors into the British navy; that is, the British were kidnapping American sailors and forcing them to serve in the British navy.
Another argument dealt with the fact that American ships were being seized by the British. The British and French were at war and the British were capturing American ships headed towards France.
Others felt that war with Britain would end the troubles Americans were having with Indians on the frontier. Many felt that the British were arming and inciting the Native American Indians to attack American settlers.
Finally, some argued that war was necessary to maintain American sovereignty and to restore national honor, both of which had been attacked by the British actions on the high seas and on the American frontier.