Explain why new Englanders protested the war

Great Britain was in constant war with France, Napoleon's rule. Britain wanted to eliminate the supplies that come to US from France. It restricted the traded relationship between America and France. This annoyed the Americans. Britain required Americans to get the license from it in order to extend a smooth trade with France.

The British Navy made the American troops to surrender and by force made them join their Navy; this is called impressment of Americans by British Navy.

President James Madison ordered the Government to wage a war against Britain as it weakened the relationship of America with its allied powers.

Despite having led the charge in the Revolution, New Englanders were vehemently opposed to America's second war with the British ... Ellis says following a particularly bad incident in 1807, the States were so united in their anger against the British that they probably would have marched to war in lockstep.