Speaking to journalists in-flight on his way back from Strasbourg, Pope Francis touched on dialogue with extremist terrorists – saying that although it's difficult, the door is never completely closed.

"Never give up anything for lost, never. Possibly you can't have dialogue but never close a door," the Pope said in response to a question posed by international reporters on the papal plane Nov. 25.

Although dialogue might be challenging – "you could say almost impossible" – the "door is always open, no?"

Pope Francis responded to six questions posed to him in Italian during a brief press conference held on his return flight from Strasbourg, France, where he addressed the local seat of European Parliament as well as that of the European Council.

In his response to the question on terrorism, posed by Andreas Englisch from Random House, the Pope noted how the journalist twice used the word threat when asking about "the terroristic threat and the threat of slavery," particularly the slavery of human trafficking.

"It's true. Terrorism is a reality and also a threat. But, slavery is a reality inserted in the social fabric of today (and has been) for a long time," the Bishop of Rome observed, saying that the phenomenon of human trafficking is "a drama" that often involves the sale of children.

He encouraged the handful of journalists present not to "close our eyes" to the daily reality of slavery, which exploits people.

Terrorism, on the other hand, has another aspect besides the terrorists we are familiar with, and that is "the terrorism of states," the pontiff said.

"When things increase more and more and every state, for its part, feels the right to massacre terrorists and with the terrorists there are so many innocent people who fall. This is a high-level anarchy which is very dangerous."

He explained that terrorism needs to be fought, and repeated what he said during the in-flight press conference on his way back from South Korea: "When you need to stop the unjust aggressor, you have to do it with international consensus. No nation has the right to stop an unjust aggressor on its own."

Pope Francis had spoken about the presence of terrorism in both of his speeches for the day, first telling members of the European Parliament that by holding true to their religious roots, they would become "more immune to the many forms of extremism spreading in the world today."

The Pope said that this extremism is due in large part to "the great vacuum of ideals" that are currently being espoused in the West, and warned that it is primarily because of "man's forgetfulness of God and his failure to give him glory" that such violence arises.

In his speech to the European Council, the Pope said that peace is often "put to the test" by various forms of conflict, including religious conflicts and international terrorism which claims the lives of innocent victims.

This terrorism is "unfortunately bankrolled by a frequently unchecked traffic in weapons," he noted, and condemned the ongoing phenomenon of the arms trade, as well as that of human trafficking.

During his return trip from Strasbourg Pope Francis also responded to a question from Spanish-speaking journalists regarding the current situation unfolding in Granada, Spain, in which three priests have been accused of abusing a youth over a decade ago.

The alleged victim, now a 24-year-old man, wrote a letter to the Vatican speaking of his abuse. He eventually received a call from Pope Francis, who encouraged him to go to local authorities, and has already filed a lawsuit against the 3 priests, who have been removed from their ministry.

In addition to the Pope's words, the young man has also spoken to Granada's Archbishop Javier Martinez Fernandez, who has been in contact with Vatican officials since mid-August.

When asked how he received the news of the alleged abuse, Pope Francis said that he took it with "great sorrow. Really deep sorrow. But, the truth is the truth and we shouldn't hide it."

The Pope said that he called the young man and told him "you go to the bishop tomorrow," and also wrote the bishop telling him to "begin the work, to make an investigation and move forward."

In addition to these topics, Pope Francis also discussed his devotion to St. Joseph, his return to France for a longer pastoral trip next year, and how the social doctrine of the Church aligns with the Gospel rather than a political party.

Before retiring for the rest of the flight, the Pope thanked journalists for their work on a "truly busy day," and asked again for continued prayers.

Andrea Gagliarducci contributed to this report.