Maybe coz some muslims kills more frequently than ppls of any other religion. maybe coz They kill their own ppls more frequently and than quote religiuos scriptures to justify their act. Maybe U wont find as many groups as among muslims which have been created only to wreak havoc over their fellow human beings.
Although blaming Islam for their henious act has no justification at all, but muslims cant shrug off their responsibility, its their duty only to tell to the world what Islam is all about, and they misrably failed in this job.