Dresden do have a history of having a Neo-Nazi element to their ultras. But still
http://inbedwithmaradona.com/journal/2011/10/25/reconstructing-an-identity-this-is-dynamo-dresden.html
Edit: Here's the same incident from the Dresden end, where they were chanting about Frankfurt being Jews, which might be what prompted it.
www.youtube.com/watch?v=eyAYPNznQZA