Because it’s totally un-Islamic (United Kingdom)

https://www.youtube.com/watch?v=hAxIOC8Zisc 

The Active Change Foundation, based in East London, is a community based organisation set up to protect and safeguard young people and families from unrest and violence in all its forms.

#NotInMyName: Young British Muslims at Active Change Foundation show their solidarity against ISIS and their actions. See how a simple message can be shared to show how ISIS is misrepresenting Islam. Join the movement by tweeting why ISIS does not represent you with the hashtag #NotInMyName.

Source: Active Change Foundation