If you had the ability to travel back in time, would you prevent certain events from occuring?

For example, prevent JFK from being asinated, prevent Judas Iscariot from turning in Jesus, prevent the hijackers from crashing into the WTC, prevent Hitler from rising to power, alert the US Navy of the Pearl Harbor attacks, prevent Lincoln from asination, prevent Africans from becoming slaves, prevent Mohammed from spreading Islam, prevent the asination of Martin Luther King, prevent the spread of HIV/AIDS, prevent the great fires of Chicago and London, prevent Jack the Ripper from killing, prevent Jeffrey Dahmer from killing, prevent the Russian work camps of Stalin, prevent the rise of Communism, etc.