The phrase refers to a notorious track by the underground German hip-hop group (the successor project to the banned neo-Nazi band Landser).
In the early 2000s, sites like Napster, Limewire, and BearShare were flooded with poorly labeled MP3s. A search like "am tag als ignatz bubis starb mp3 best" is a relic of that era—a time when users had to specify they wanted the "best" version to avoid low-quality radio rips or virus-laden files.
For historians and researchers of the "Rechtsrock" (Right-wing rock) scene, finding a high-quality audio file is part of documenting the evolution of extremist propaganda in the digital age.
The taboo nature of the track often piques the curiosity of those interested in the darker corners of German musical history. The Evolution of the MP3 Search