Why are attacks by Islamic groups called Islamist terrorism? Other terror groups like the LTTE (Tamil Tigers) or the IRA (Irish Republican Army) have Hindus or Christians but are not called Hindu or Christian terrorists?
It is undoubtedly true that there are other terrorists as well, for instance the Naxalites or Maoists. The reason why the adjective 'Islamists' is used is that no other terror group invokes religious sanction or quotes religious texts to justify their acts. In fact, the Tamil Tigers has Hindus as well as Christians (their spokesperson for many years was Anton Balasingham, a Christian). Neither has the IRA nor Tamil Tigers ever quoted any religious scriptures to justify their actions, the Islamists have and continue to do so. The link between religious places and schools to these acts, is also well established.
Finally, the Islamist terrorists themselves have time and again openly admitted the religious nature of their ultimate goal -- Islamisation. It would be dishonest if this reality is ignored.