Honestly I don't see any difference between a racist group and a "terrorist" group. The issue that will come into play is how your members treat other players in a non-roleplay context and the image that it portrays to new players. With that in mind, if permission is given, I would suggest having a lengthy and thorough screening and recruitment standard of who is allowed to represent your group. The last thing you want for your group or the server is a bunch of new players coming in and seeing "white supremecy" as being tolerated so they can start flaming in /p. Additionally, I would recommend establishing a safe-word to mutually disengage both parties from the roleplay prior to any interaction. Just as sexual roleplay is ALLOWED as long as both parties agree, if one party feels uncomfortable or offended by the groups actions or statements within the RP, they can state this to the other party, and if they continue, then it becomes an Administrative Matter and can lead to punishments.