The Soldiers of Odin will crush the heathens beneath their boots.
The (War criminals) of (A "God" from a terrible fanfiction of an actual religion) do not stand a chance, and therefore should absolutely meet their ends at the hands of the (superior) Soldiers of Odin. They can go back home if they don't want to die.
To intentionally give rise to conflict by meeting force with force invites only pain and suffering to all parties involved. It does not make sense to lead campaigns of war in the name of peace. Defend yourselves, improve the lives of your people, and seek peaceful interactions with all to defuse situations before the need for military action arises.
The soldiers of Allah may have their religious zealotry on their side, but they do not have the numbers, skills, not to mention the anger that has built up in the Odin Soldiers, due to the sexual assaults, vandalism, ungratefulness and sheer barbarity that the refugees have brought along with them.
The decision of the Soldiers of Allah to take on the Odin Soldiers would only further the animosity towards Muslim immigrants in Northern Europe and around the world. It would make the lives more difficult of peaceful Muslims trying to make a life for themselves in the Western World escaping their wartorn lands.
Regardless of reason or justification. Vigilante justice is black and white. When two radical groups clash, expecting peace is among one of the most foolish things to do. Violence will most definitely be a huge issue once the two parties collide, there will surely be many innocent casualities who don't wish to be involved but are caught up in the fire.