>Who? When? Where?

The CCC and most of its members - and they don't exactly hide it. The CCC founder was on the far left and that's exactly the course it took.

They have talks by Antifa activists. They have combined CCC and Antifa logos hanging in their centers: https://twitter.com/DandelionInaBox/status/90147462783431884...

German Antifa are about as extremist as it gets and they are rightly watched by the state police. They threaten and attack citizens and police for political reasons and do about everything else that's considered extremist.

tl;dr: Left extremism is openly accepted by the CCC.

Now you can downvote this post too, but these are verifiable facts.