America doesn't give a shit about country borders.

If this ISIS avatar is illegal in several countries around the world, then either block those countries IP addresses from accessing this site so this guy can keep his avatar, or ban his avatar.

The site is being hosted in the US, so I'm assuming they're abiding by American laws.

I have a question for you though; is CBC.ca blocked in the Netherlands? They're often running stories with images or videos that include the ISIS flag. According to your logic, CBC.ca, or at least the CBC.ca stories on ISIS should be blocked when they're trying to be accessed on a Netherlands IP. Hint: Neither CBC.ca, or the ISIS articles on CBC are blocked on Netherlands IPs. I see no problems with this forum allowing images of ISIS flags, because I suspect if CBC is allowing anyone worldwide to see the ISIS flag, Bitcointalk won't get in any trouble for doing the same.

I don't agree with having an ISIS flag as an avatar, but there's a great ignore feature on this forum so that you don't need to see that avatar, or any posts from that user anymore.