Fr Daniel arrived in London to deliver a petition on Wednesday which urges the British Government not to ignore the plight of persecuted believers and other minorities in the region, many of whom have fled extremism and conflict.
In taking over areas in Iraq, including the sprawling city of Mosul in the Nineveh Plains, IS forced primary and secondary school-age children to undergo a radical school curriculum.
Fr Daniel, who now supports traumatised children, said: "They planted something very deep in their [the children's] minds and it will take a very, very long time to remove all of these ideas."
The 27-year-old from Erbil joined the anti-persecution charity Open Doors UK in encouraging ministers to commit to helping refugees and internally displaced people return home, as IS is gradually forced out.
Asserting that the Iraqi church is ready to engage in the rebuilding and reconciliation efforts, Fr Daniel also said: "During the time of displacement when they were staying in the [refugee] centres, those people [believers] were taught and were healed from their trauma.
"Now, they have more resilience so they can deal better with these cases."
His petition, signed by 750,000 in 143 countries, urges that the rights of Christians and other minorities as citizens of Middle Eastern countries be recognised, and that they have access to "dignified" living conditions.
The document, which forms part of Open Doors' Hope for the Middle East campaign, will be presented to peers and MPs in the House of Parliament.
Click here to listen to Premier's Alex Williams speaking with Fr Daniel: