VATICAN CITY -- Pope Francis on Sunday lamented what he called a "culture of insults" enabled by social media and warned against nationalism and other "exclusivist ideas" that he said contrast with a Christian mission to foster harmony.

In his homily during Pentecost Mass Sunday in St. Peter's Square, Francis also decried that "the more we use social media, the less social we are becoming."

"In today's world, lack of harmony has led to stark divisions," Francis said. "There are those who have too much and those who have nothing, those who want to live to a hundred and those who cannot even be born."

He warned of the temptation to cling to "our little group, to the things and people we like," concluding that it's only a "small step from a nest to a sect, even within the church."

The pope said that "nowadays it is fashionable to hurl adjectives and, sadly, even insults" in what's tantamount to "a culture of insults." He recommended responding "to malice with goodness, to shouting with silence, to gossip with prayer, to defeatism with encouragement."

He also warned against the Catholic church's neglecting its mission to spread joy, instead becoming an organization with propaganda as its mission.

The Vatican after Mass released a papal message about the church's mission in the world. In it, Francis echoed a call a century ago by Pope Benedict XV, right after the devastation of World War I, for "an end to all forms of nationalism and ethnocentrism." He also cited a reminder by that same pope that "the church's universal mission requires setting aside exclusivist ideas of membership in one's own country and ethnic group."

Said Francis as he defined the church's mission today: "No one ought to remain closed in self-absorption."