Re: the Horst Wessel Song. I am always in favor of reclaiming good tunes from the bad guys. The melody had an honorable history before the Nazis adopted it with new lyrics. It’s past time to take it back. Deutschland Uber Alles is another good example. The melody is by Hayden and, as a hymn, the tune is a standard in musically competent churches. The version that was adopted as the national anthem in the 19th century was a call for German national unity. It was not directed against foreigners at all; it called for Germany “over” Bavaria, Saxony, Prussia, and all the other formerly independent German states. It’s a fine tune and one of the best national anthems. Lyrics can always be readjusted.
The other example is the Russian National anthem, which was adopted from the old Soviet anthem with new lyrics. Probably still musically the best anthem of all (well next to the Star Spangled Banner, of course)