I went through YouTube's copyright dispute process, and said it was a fair use derivative work. YouTube's response is apparently to ask the copyright owner if they feel it's fair use. Which, of course, they didn't.
Ironically, it was LMFAO's label that had the problem, and yet LMFAO posted the song to their Facebook and Twitter profiles. C'est la vie.
The original PSY Gangnam style video is blocked in Germany, so I don't think your dispute will have any effect. Can you make it available for download? I would really like to see (and hear) it.
What cases are you talking about when you say "like this one"? There absolutely is no statutory fair use protection for mashups in the general case, and I'd be shocked if the case law is anything but subjective.
Ironically, it was LMFAO's label that had the problem, and yet LMFAO posted the song to their Facebook and Twitter profiles. C'est la vie.