Express disbelief that someone would join a chatroom associated with a terrorist group, and express skepticism that their stated reason for doing so is genuine.
I don't care how curious you are about ISIS or any other terrorist group....why the heck would you go and digitally mark yourself in that chatroom? And to say he is curious is crap....the dude already went into the FBI building and said he was being "forced" to watch ISIS crap. I don't care who you are, if you don't see it for what it is, you are ignorant.