Many years ago my lecturer, Professor Stevan Harnad drew the line at backbones, if you have a spine or similar arrangement it's not OK to eat you. These days Harnad is a Vegan, which entails prohibition against a much larger array of animals being eaten or indeed taken advantage of in any way for your benefit.
There is no reason to imagine that if there was alien life it would be able to comprehend us at all, for fictional convenience it has been usual to depict aliens as basically just humans in Halloween costume and there is every reason to assume they would be entirely incomprehensible instead. Even in soft SF, try say Iain M Banks' repeated reference to other forms of life which show essentially no interest in the scale of events that our human-like characters are engaged with. The Stellar Field Liner, a vast entity living in the magnetosphere of a star, the Excession, seemingly a living portal to other universes, or even just the Dirigible Behemothaurs which are island sized creatures that think a Galactic Cycle (225 million Earth years) is not very long.
Mm.
So, are The Affront the literary equivalent of a human in a halloween costume? Extreme sadism as the only definiting trait I can recall, so they probably count as Planet of Hats* even if the physiology is too different to be a costume department's job in a TV show.
Sure, it's really hard to do SF where you have aliens and keep them alien, because they no longer fulfil ordinary plot parameters. The key characters in the parallel story in Greg Egan's novel "Incandescence" aren't humans, never have been humans, and they live somewhere that humans would immediately die horribly and we'd need an XKCD "What if?" discussion to figure out how they die exactly 'cos they're much too close to a collapsed star and there's also no Oxygen and you can bet everything is totally saturated in radiation... They're probably... tiny? Nevertheless, they're our protagonists for fully half of a novel, so, they're going to get humanized.