One of the main arguments that colonizers used to justify how they took control over the new territories that Columbus discovered in 1492 in the so-called "New World", was that their main purpouse was Evangelism.
Evangelism is the denomination of the process that consists on extending the teachings and principles of the Christian religion worlwide. Therefore colonizers were complying with their duty as Christians of spreading the message of Jesus Christ among the pagan native civilizations encountered in America.