The Islamic State released a video earlier this month showing a group of Arab jihadists on a slaughtering frenzy in eastern Syria. On the floor were several tied-up Syrian rebels, prepared for the knife. "The best thing about what you did is that you started with the Military Council, no question about this one," says an Egyptian member in jest, referring to the killing of a fighter affiliated to the Free Syrian Army, deemed by Isis as apostates for working with the west. A Tunisian member then raises the head of his next victim and tells him: "Brother, you will be slaughtered now, brother." The Egyptian then tells his colleagues that the videos should not be uploaded to the internet, to which the Tunisian replies: "Brother, I like these scenes. I like to watch them at night."

The video received little international media attention, compared with last week's gruesome murder of the American photojournalist James Foley. But it was widely circulated in the Middle East as the scene of Isis jihadists joking and laughing about their victims revealed a new level of barbarity to the group. It was not only cold-blooded but also sadistic. Those who have often justified the group's barbarity as a necessary aspect of wars saw a different face.

The two murders, in a morbid way, united the east and west against Isis. In the region, the killing of Foley was widely condemned. Many took to social media to offer condolences to his family, mostly emphasising that people in the region, primarily from the religious sect Isis claim to represent, have suffered from the group in the same way. Many, however, objected to the west's readiness to act against Isis despite the fact that Isis have killed and slaughtered thousands of people, displaced whole villages and demolished places of worship.

Despite these actions, people have contrasted the west's response to Foley's killing by being ready to strike Isis's bases with the lack of appropriate response to the havoc Isis systematically wreaked for months in the region against Syrians. They pointed out that some of the most atrocious killing happened as the US was preparing to intervene to save stranded Yazidis in northern Iraq.

But despite the ambivalence towards the west, people and politicians in the region have been unequivocal in their condemnation of Isis. Last Tuesday, Saudi Arabia's grand mufti, Abdulaziz al-Sheikh, described Isis as Islam's "enemy number one" and called for "decisive" measures against clerics who lure young Saudis into extremism. Even radical clerics associated with al-Qaida have made unparalleled statements about the group. Abu Mariya al-Qahtani, until recently the second top official at Jabhat al-Nusra in Syria, asked al-Qaida to "apologise and repent to God" for failing to speak out against the extremism of Isis's predecessors in Iraq. The failure to condemn their acts in Iraq was, he said, a direct cause of the group's extremism today. Atiyatulla al-Libi, an al-Qaida ideologue from Libya, said that the indiscriminate killing of innocent Muslims did not represent jihadism."

Politically, there seems to be a race throughout the region over who is better positioned to fight Isis. Riyadh pledged $100m to the UN's centre to combat terrorism to counter what officials called "an evil that affects us all". Kuwait has taken steps to shut down some Islamic charities suspected of sending money to jihadists. Last Wednesday, Kuwaiti authorities arrested suspected jihadi financier Hajjaj al-Ajmi before releasing him a day later. Even the PKK, listed by the Americans as a terrorist organisation, has been pushing to reverse the designation since it has been fighting against Isis in Iraq and Syria. Iran and its allies in the region, on the other hand, have been more assertive in presenting themselves as a viable partner against Isis. The Syrian regime has uncharacteristically started bombing Isis bases in Syria, long spared the bombardment that affected other rebel factions and territories.

Reading the regional shifts in alliances might seem bewildering but the shifts themselves can be hugely significant. According to Arab and Kurdish sources, the crisis has led to closer links between Tehran and the president of the Iraqi Kurdish region, Masoud Barzani. A Kurdish source told me the reason for these improved ties is Iran's quick move to assist the Kurds in their fight against Isis, unlike Arab allies who merely provided humanitarian assistance.

Hezbollah leader Hassan Nasrallah, in an interview with the Lebanese newspaper Al Akhbar, used the opportunity to reiterate two messages he has made in the past. The first is that without his party's involvement in Syria, extremists would have marched into Lebanon. The second is to present his party, along with its patrons and allies, as a regional force against takfirism, a term that usually refers to radical Sunnis. In the wake of its military involvement alongside the Syrian regime to repress a popular uprising, Hezbollah's decade-long perception in the region as a resistance force started to unravel and its sectarian position prevailed in people's minds.

But the party quickly adopted a new rhetoric; anti-takfirism ensures that Hezbollah wins influence not only among minorities but also from moderate Sunnis who equally fear the rise of groups such as Isis. This strategy is slowly coming to fruition.

The predominance of Isis as a regional concern for most forces has also led to a slight, yet important, regional realignment, with Qatar and Turkey moving closer to the Saudi position of prioritising the fight against extremism, particularly in Syria. The Saudi position itself is edging closer to the Iranian one, of not seeking the downfall of the Assad regime – at least, not now.

This past week was one of drawing parallels. Saudi Arabia's top cleric condemned Isis's behaviour, but authorities there have beheaded at least 19 convicts since 4 August. Many of those who condemned the summary execution of Isis rivals celebrated Hamas's execution of 18 suspected informants. While the world's attention was focused on Isis, a like-minded Shia militia attacked a Sunni mosque in the Iraqi province of Diyala on Friday, killing nearly 70 worshippers. This militia is linked to the government and has fought alongside the security forces against Isis.

The American defence secretary, Chuck Hagel, warned last Thursday that Isis is "beyond anything that we've seen before". And yet the causes that led to the rise of Isis are all too familiar. And the Americans have contributed their share to these causes.

Isis thrive on the inconsistencies and injustices that plague the region. A response to Isis cannot involve, for example, working with a government-linked militia that indiscriminately kills worshippers, while rhetorically recognising that a credible and viable political process is necessary for Iraq. Nor does it involve flirting with the Assad regime to fight Isis after it killed or caused the death of close to 200,000 people. The battle against Isis, which itself came on the heels of failure to address the root causes of al-Qaida before it, has to be far-reaching and consistent. Otherwise, the defeat of Isis will only give way to an even more extreme and formidable force.

Hassan Hassan is an analyst at the Delma Institute, a research centre in Abu Dhabi