>because they lack X they are not worthy of consideration. It’s okay if they suffer. This is precisely the same logic that was used to justify slavery, for example.
Wowzers, this is the most strawmanny characterisation of this view I think I've seen outside of scifi villains in B movies. I don't think the most charitable view is that species "deserve to suffer." It's that they have different capacities for suffering, and that differences in the complexity of the nociceptive and the nervous systems are inputs into our understanding when we try to figure this stuff out. That leads to, say, jellyfish being treated with different moral urgency than mammals, or eggs being treated differently than hatched birds.
The B-Movie scifi villian characterization also is problematic not just because of it's anti-intellectual shallowness, but also because it considers moral assessment in it's negative sense but not it's positive. Namely, that this is about tending to the needs and moral well-being in cases where the urgency in protecting it is greatest, and we can make good choices to do the most good. We make choices that prioritize the well-being and safety of our children in ways that take their well-being seriously, and we prioritize saving our children from a burning building in a way that we don't prioritize saving the mice living in the basement of that burning building. To treat them equally, or to prioritize the other way around, would find someone facing the moral condemnation of the community as well as legal consequences, and nobody would be convinced to withhold those judgments by speeches about speciesism.