Unfortunately bitcoin is often used for illegal activities including terrorism and itt anonimity contributed great deal to that. That is the reason why bitcoin had bad reputation very long time, some even considered it as a criminal currency although every currency in the world could be used for crime.
I do not think that it is a terrorist currency and I know that not much of the illegal activities are done with bitcoin because bitcoin is a new currency and for the understanding of it we require a good knowledge . I want to say that well educated people can adopt and handle bitcoin and these educated people are not involved in crimes and the terrorists are not much educated so they will find it hard to adopt.