You can also use a symbol in modified form against the group using it.

For example by crossing it out, for example, or by using it in a caricature where one compares it with trash.

This symbol https://upload.wikimedia.org/wikipedia/commons/c/c2/Anti-Naz... obviously contains a swastika, but is obviously legal even under current German law, as it does not encourage Nazism

If only it was so obvious. There was a case in 2006 I remembered were it apparently wasn't quite so for some people, http://www.dw.com/en/german-company-fined-for-selling-anti-n..., don't know if something similar came up again more recently.

The case you linked has been reversed by a higher court, though. And a German federal politician who was involved in that suggested a change in the law, but the government was against it.

Yeah, these days it's primarily usa-based white power groups.