User blog comment:IamJakuhoRaikoben/Chapter 361: The Two Bombs, Review./@comment-5668006-20131123040415/@comment-24066070-20131123103410

Or maybe demons have a curse by default, but are still capable of learning magic if they are interested in it. Silver may have foudn a book about Ice devil Slayer magic and thought "seems cool, imma learn it".

Jackal may have also been arrogant and wanted to point out that their magic is superior to that of "ordinary" mages. Like how Hades considered the Seven Kin far superior due to their lost magic. Could be something like a rich person who wears expensive clothing and doesn't consider an ordinary T-shirt to be clothing.

But then again, as we've both said, we don't know enough about them. Therefore I think it's good to keep all sorts of possibilities in mind.