Yea if it will be so popular in terrorist world then all exchanges based in civilized countries will be force to stop trading it.
All people who will have open xmr wallet will be juge as terrorist and you will see that masses 10 person per day able to use XMR.
Do you think that any government will allow such tool to exist,they will put in prison for having XMR client in computer.
You will see liquid of XMR hmm bugattis which are sold once per year at dealer if goverment will ban such coin.
Terrorism is good ecscuse for them for more control in USA currently you can go to jail without court for forever because they suspect that you are terrorist.
If they target XMR as terrorist money GL to that coin. Dev will land in prison as well as it was with guys who was developing disk encryption.
They claim that disk encryption is weapon and he went to jail .
You won't hide with your xmr in hole dark net is nice marketing stuff but it can be really death blow at end for coin.

PS: A day when XMR would be popular in terrorist community its best day to sell IMO.