In the last days of 2015, Human Rights Watch (HRW) published a report entitled If the Dead Could Speak. The result of a painstaking nine-month investigation into more than 28,000 photos smuggled out of Syria by a military defector, it documented evidence of widespread torture, starvation, and disease in Syrian government detention facilities.

You are warned, before looking at the gallery of photographs online, of distressing content. Bodies are emaciated; faces bruised and bloodied.

The process of verification was a grim one. Human Rights Watch interviewed family members who had spent months, or years, searching for news of their loved ones. They included Dahi al-Musalmani, who identified a picture of his nephew, Ahmad, a 14-year-old who disappeared after officers found an anti-Assad song on his phone.

Ahmad is one of more than 117,000 people arrested and detained in Syria since the beginning of the uprising in March 2011, according to estimates by the Syrian Network for Human Rights. Human Rights Watch believes that the photographs represent a "fraction" of those who have died in custody and that the use of torture in Syria is "so widespread and systematic that they indicate a clear state policy, meaning they constitute crimes against humanity."

In the same month that this report was published, articles appeared in the Daily Telegraph urging the British Government to practise some realpolitik in its dealings with Syria.

"Let's deal with the Devil," wrote Boris Johnson. "We cannot afford to be picky about our allies."

In arguing in favour of airstrikes in Syria and working with Vladimir Putin and Bashar al-Assad, he explained that he didn't want the victims of ISIS on his conscience. Close to his heart, too, is Palmyra, the UNESCO world heritage site facing demolition at the hands of the militants.

"Am I backing the Assad regime, and the Russians, in their joint enterprise to recapture that amazing site?" he asked. "You bet I am."

Missing from Johnson's account was any explanation of how the "devil" Assad got his name. There was no mention, for example, of the fact that the regime is the biggest killing machine in Syria, responsible for far more civilian deaths than any other group. No reference to the oil drums packed with explosives and metal shards raining down on neighbourhoods, the "widespread violations of human rights" condemned by the UN Security Council, or, indeed, Assad's role in the growth of the very extremists the airstrikes are designed to eliminate.

Johnson is right that Islamic State must be defeated, but those making the case for a pact with the Devil need to be clear about exactly who we are dealing with. In recent weeks, I have been taken aback by the extent of ignorance about the Assad's regime. Perhaps I should not be surprised. While Islamic State revels in disseminating evidence of its atrocities, the Syrian government is engaged in a campaign of denial and distortion. It has learned over the course of the past five years that it can ignore UN Security Council resolutions and bomb civilians with impunity. Witness Assad's amused response when asked by Jeremy Bowen last year about his use of the aforementioned barrel bombs 

With Assad's accountability not even on the agenda at the current peace talks, we owe it to his victims to learn the truth about his actions and to echo their demands for justice, however long it takes to arrive. We can start by remembering the origins of the uprising in Syria. The protests first broke out in Daraa in response to the detention and torture of children accused of painting anti-government graffiti. When the parents of Hamza Khatib, a 13-year-old boy, collected his body they found it mutilated, and covered in bruises and cigarette burns. The demonstrations were overwhelmingly peaceful but the government responded to its people's demands for democracy, justice, and the rule of law, with shelling, arbitrary arrests, disappearances and systematic torture in detention. Human Rights Watch has interviewed families who saw their unarmed relatives mown down by government and pro-government forces. It has also gathered evidence of chemical attacks by government forces. A UN report into a massacre at Houla in 2012 found that Government forces were responsible for the killing of more than 100 people. Amnesty International reports that "all had been shot dead, except for a few children whose skulls had been smashed, presumably by rifle butts".

The regime's narrative that it is a bulwark against terrorism also requires scrutiny, for Assad is an arsonist posing as a fireman. In 2011 he released from prison jihadists who had fought in Iraq while retaining in detention those who had supported peaceful protests. He was then able to claim that the uprising was orchestrated by foreign-backed extremists and to present himself as the solution to the violence. This article explains this strategy, including how Assad left IS to construct its "caliphate", while focusing his attention on other elements of the opposition. Researchers from the International Centre for the Study of Radicalisation have explained here how his regime has "repeatedly and deliberately conspired in killing some of its most vulnerable citizens" and argued that any attempt to rehabilitate him in the eyes of the international community would be "morally bankrupt."

Where do Syrian Christians fit into this? How should we respond when we see pictures of smiling churchgoers attempting to take selfies with Assad just before Christmas? Or when a Syrian archbishop pleads with Britain to stop backing opposition to the President? Can we really expect Christians, a vulnerable minority in the Middle East, facing an existential threat from extremism, to speak out against a man who promises them protection and, occasionally, arrives as liberator?

There are good reasons why some Christians express nostalgia for the Syria they knew prior to the Arab Spring and why they fear what might follow the removal of President Assad. It is not that church leaders are blind to the moral ambiguity of their position, as this article explains. Nadim Nassar, a Syrian Anglican priest, offers a useful corrective to those who demand that Christians in the region back calls for regime change. Such rash action could result in a vacuum filled with violence.

But we also owe it to civil society activists, such as Bassel Shehadeh, killed during a government attack on Homs, to learn the truth about Assad's regime, to speak out, and to pray for justice as well as peace. It is easy to get the impression from media reports that Syria is devoid of light or hope. New Internationalist has done an excellent job of giving a voice to "Syria's Good Guys". I also recommend watching A Syrian Love Story, which follows two activists involved in the early days of the uprising.

"Many of the former detainees who were held in these nightmarish conditions told us they often wished they would die, rather than continue suffering," HRW's Nadim Houry said, at the launch of If the Dead Could Speak. "They begged countries involved in seeking a peace process to do everything they can to help the people still being held in Syria."

With peace talks now underway, let us call for justice and truth-telling and remember those who no longer have a voice.

Madeleine Davies is deputy news editor of the Church Times, writing in a personal capacity. Follow her on Twitter.