Assuming it is permitted to listen to music composed or performed by a non-Jew, is it prohibited, ill-advised, or outright permitted to listen to instrumental secular music by a composer who unabashedly hates Jews?
Though I don't have the original before me, the Journal of Halacha and Contemporary Society (Volume 14), cites the following1 from Rabbi Hayim Dawidh Halewi (עשה לך רב כרך ג פרק ד):
Secular music written by a wicked person, such as Wagner, is permitted as long as it does not endorse evil in the language (verbal or programmatic) of the music itself.
1. This opinion pertains to recorded music. Without studying the original, I am uncertain if it pertains to live music.