I also take issue with that statement. I've been to Christiania 3 times as a tourist and the drug market looks about as diverse as Copenhagen in general. Also, I've never been able to figure out who is a tourist like me, and who is dealing drugs or acting as a lookout. Nor can one tell the religion of a person simply by looking at them.
Oh and they were the ones who told you there was an "exclusively muslim criminal element"? Because the police claims the hash trade is largely controlled by the biker gang Hells Angels - but maybe your investigations have uncovered better information?
