Why did kentucky support the idea of nullification

Kentucky supported the idea of nullification because the administration of second president John Adams had passed the Alien and Sedition Acts.  

From about 1798 to 1800, the United States and France were practically at war despite a longtime alliance.  In response to actions taken by France, many Americans viewed France as an enemy.  The French Revolution and a possible war with France made Americans more suspicious of foreigners in the country who were not citizens.  Congress responded by passing strict laws to protect the nation's security.  The Alien and Sedition Acts allowed the president to send aliens (foreigners) to jail if considered "dangerous" and made it a crime to speak, write, or publish criticisms of the government.  

Two states, Virginia and Kentucky, believed these laws were unconstitutional because they violated individual rights to free speech, free press, and the right to a fair trial.  Kentucky suggested that states should be allowed to nullify (or legally overturn) federal laws that were considered unconstitutional.