Archbishop Justin was delivering the sermon at a special service for journalists who have died while reporting from conflict zones which has been held at St Bride's Church on Fleet Street in London.
It was the first time an Archbishop attended the event that has been taking place at the venue for the last seven years.
According to the Guardian, Archbishop Justin said frontline reporters were the "lookouts who stand on the watchtower" and paid a "profound cost" for what they saw, "sometimes deeply hurt mentally, emotionally, physically, spiritually, even killed doing it.
"It is right and essential that we give thanks for those who witness, who unlock the covers of the wells of compassion that can become available, who challenge the complacency in which some people suggest that we can live in our own country as though the rest of the world did not matter."
Archbishop Justin said his experience of conflicts and meeting war correspondents "leads me to suggest, controversially, that it is just a little bit possible that they are not all entirely saintly at every minute of the day.
"But there is an old saying in the church ... the fact that the priest is all messed up does not mess up the sacrament."
"We live in a world where it feels as though the darkness is falling ever more severely on whole swathes and regions and in which the light of the news often seems to go out", he said.
"There are whole areas where there is fighting that is forgotten because there is so much of it, whole areas which depend on the likes of James Foley and Steven Sotloff [the US journalists murdered after being kidnapped by Isis in Syria] to show some light on what is happening."
He also praised the "extraordinary value" of frontline reporters covering overseas conflicts and the Ebola crisis for shining a light on "this darkening world."