Here again, the problem has nothing to do with a person's religion, but on a given behaviour that makes the practise of aikido in its full sense impossible. After that, if that person is a rabid supporter of the Taliban, of Torquemada or of Stalin, as long as he keeps it out of the dojo, it's not the dojo's concern anymore. After all, Ueshiba met and practised with many people with very debatable views on their nation and its place in the world.
No, I think it is important to sometimes take a holisitc view of the person. If I had verifiable knowledge that someone did not represent the values that we aspire to outside the dojo as well, then I would ask them to leave.
Being a Terriorist is definitely one of them and I think it is our business.
An extreme example for sure, as folks don't usually wear "Hug me, I'm a terrorist!" T-shirts.
I did have a student once that went out got drunk and kicked people's asses in bar fights for fun. I counseled him. Next time, I refused to train him any longer.
I think as Aikdoka, we have a responsibility that extends beyond the hours and walls of the dojo.