Animal welfare laws don't give atheist butchers the option to be cruel. They're required to stun the animal first. Why give halal/kosher butchers the option to be cruel? Especially if you claim "most do" choose to stun.
Be kinder to animals, change "most do" to "all do" by removing the religious exception.
...and then come the progressive types to defend 1000+ year old ritual slaughter customs.
I’m not saying I endorse this, but that is why.
What's objectionable about halal?
It's really not. You're mixing two things, "max-capitalism factory farming" alludes to how the animal is treated while it's alive, e.g. caged hens vs free-range hens, while what we're talking about here is animal suffering via religious ritual slaughter.
Kosher and halal slaughter are not animal-friendly. They mandate cutting the animal's throat but preserving its spinal cord so it feels every possible pain in its last moments alive as the blood drains out.
Stunning it before death and/or putting a bolt through its brain would be a lot more humane, but those methods didn't exist when those religions came up their rules, so of course not one iota of progress can be added.
Read more about it:
https://en.wikipedia.org/wiki/Dhabihah
https://en.wikipedia.org/wiki/Shechita
https://en.wikipedia.org/wiki/Legal_aspects_of_ritual_slaugh...
https://en.wikipedia.org/wiki/Electronarcosis
https://en.wikipedia.org/wiki/Captive_bolt_pistol
You'll see that authorities in e.g. the UK have been asked to regulate kosher/halal butchers, require them to at least stun the animal before doing their ritual slaughter... and the authorities chose not to, and let them keep their religious exemption to animal cruelty laws. Kosher and halal slaughterers can choose to stun the animal first, which would be humane, but they don't have to.
The fact that kosher/halal are very similar is a hilarious wrinkle for the culture war aspect that OP was pushing.