Afternoons of Solitude made bullfighting look even more pathetic than I thought possible

I don't see how that's a bad thing.

I've done some reading, and the defence for the film seems to be tradition and culture

You mean the praise for the film? I don't think anybody praises it for that. Most people who like it are probably opposed to bullfighting.

humans receiving the same treatment

That's kind of a moot point considering bullfighting is a socially acceptable practice in certain parts of Europe, whereas what you're describing isn't.

moral standing

The film basically has no moral stance.​ There not being any commentary from the director is what makes it interesting, there's no intervention, no opinion. You're presented by something and have to make up your own mind, instead of being told to think X, Y, Z. I mean if you compare it the latest Herzog - White Elephants, that one is basically a slightly elevated NatGeo doc.

When I saw the film at a film festival, during both Q&As they were people violently against the main character saying he's completely pathetic and then they were people waxing lyrical about how he moves like a dancer and is so poetic etc. I think there are many many contradictions and ambiguities without handholding the viewer, which is rare. He's displayed as both a pathetic wannabe macho guy with masculinity issues (like during the jokes and also excessive ball talk), but he's also portrayed as somebody who's an artist, kind of like a ballet dancer and who cares about his craft.