We all know that Bitcoin is also popular to criminals because they can use it without exposing their identity. It will be more convenient to them to use Bitcoin so that they can hide their identity. Do you think that terrorist groups like ISIS use it for their transactions?
Why not. ISIS has a strong intelligence i think and transacting with bitcoin would likely be a good option for these no-gooders. These people obviously are not stupid and btc would already be in their radars. Sad to say, but btc's features can also be taken advantage of by evil people
They need money for their secret and public operations, they need money for weapons and for everything else. In situation they are now it's not easy to move cash around, they can't use banks so what is left? Do they use bitcoin, yes for sure, and other coins also, some other coins can provide more anonymity then bitcoin.
They use bitcoin now, tomorrow something else, they need it and they will always find a way for achieving their goals, one way or another, people can die or suffer, its their nature, bitcoin has nothing with their character.