Thomas Paine compared Britain to a thief who breaks into a house. How does he use this comparison to motivate colonists to fight?The story is named...

In "The Crisis, No.1," Thomas Paine writes

Tis the business of little minds to shrink; but he whose heart is firm, and whose conscience approves his conduct, will pursue his principles unto death. My own line of reasoning is to myself as straight and clear as a ray of light.  Not all the treasure of the world, so far as I believe, could have induced me to support an offensive war, for I think it murder; but if a thief breaks into my house, burns and destroys my properoty, and kills or threatens to kill me, or those that are in it, and to "bind me in all cases whatsoever," to his absolute will, am I to suffer it?

The analogy of the thief for the British is used by the outspoken Paine to emphasize the unfounded "offensive war" of the British against the personal rights of the Colonists.  The British were stationed in doorways, property was confiscated, men were pressured to give up their arms.  So, Paine considers them analogous to "thieves" who come into the homes of the Colonists, violating their privacy.

Analogies are used often in argument or persuasion to demonstrate the logic of one idea by showing how it is similar to another, accepted idea.