I completely agree. It sounds like the opposite of beautiful software if you ask me. Maybe it's interesting, thought-provoking, or amusing code, but not beautiful.
Beauty comes in very different forms. Not all beautiful paintings are pleasing and peaceful fields for flowers; IMHO, something can be dark, strange, even scary, and still beautiful. E.g.: The Garden of Earthly Delights[1], or It Follows[2].
I found it beautiful because I had never thought to use the language in that way before I had seen him do it. It wasn't hard to understand once you understood. :-)
I think it's perhaps not inappropriate for Ruby; it has a community that's all about 'magic' and even 'tricky' beauty. I certainly agree there are problems with this, but I also see how this is appealing in certain contexts.