An Israeli think tank “which advances a realist, conservative, and Zionist agenda in the search for security and peace for Israel.”, as claims in its website, cynically suggest that the West should not destroy completely Daesh.
As pointed in the article:
The West should seek the further weakening of Islamic State, but not its destruction. A weak but functioning IS can undermine the appeal of the caliphate among radical Muslims; keep bad actors focused on one another rather than on Western targets; and hamper Iran’s quest for regional hegemony.
Although the offensives in Syria and Iraq showed IS’s tactical capabilities, they were directed against failed states with weakened militaries. On occasions when the poorly trained IS troops have met well-organized opposition, even that of non-state entities like the Kurdish militias, the group’s performance has been less convincing. When greater military pressure was applied and Turkish support dwindled, IS went into retreat.
A weak IS is, counterintuitively, preferable to a destroyed IS. IS is a magnet for radicalized Muslims in countries throughout the world. These volunteers are easier targets to identify, saving intelligence work. They acquire destructive skills in the fields of Syria and Iraq that are of undoubted concern if they return home, but some of them acquire shaheed status while still away - a blessing for their home countries. If IS is fully defeated, more of these people are likely to come home and cause trouble.
The Western distaste for IS brutality and immorality should not obfuscate strategic clarity. IS are truly bad guys, but few of their opponents are much better. Allowing bad guys to kill bad guys sounds very cynical, but it is useful and even moral to do so if it keeps the bad guys busy and less able to harm the good guys. The Hobbesian reality of the Middle East does not always present a neat moral choice.
The unbelievable hypocrisy, cynicism does not end here:
The defeat of IS would encourage Iranian hegemony in the region, buttress Russia’s role, and prolong Assad’s tyranny. Tehran, Moscow, and Damascus do not share our democratic values and have little inclination to help America and the West.
Although ISIS has “killed thousands of people since it declared an Islamic caliphate in June 2014, with the Syrian city of Raqqa as its de facto capital. It captured tremendous international attention by swiftly conquering large swaths of land and by releasing gruesome pictures of beheadings and other means of execution.”, as this article itself admits, it calls the West to retain Daesh existence, to fight Russia, Iran and their allies because these do not share the democratic values of America and the West!
In other words, those who have created the Daesh barbarians, want to defend their "democratic" values against those who are fighting these barbarians! At this point, no further comments needed. You draw your own conclusions.