I came across the slime mould article some time ago via the Marginal Revolution blog. I do not find it in the least convincing. It seems to me they have their theory, then cherry pick and misinterpret all evidence to fit.
In short, totally agree with what you’re saying here.
My personal thoughts on the many errors in the SMTM theory here should you be interested: https://www.livenowthrivelater.co.uk/2021/09/is-the-obesity-epidemic-a-mystery-part-1/
https://www.livenowthrivelater.co.uk/2021/09/is-the-obesity-epidemic-a-mystery-part-2/
I switched from veganism to eating small amounts of pasture raised meat for these reasons.
The lives of well treated livestock do seem to be a net positive and considerably better on average than those of wild animals. Less stress, less suffering, quick and painless death.
There are some arguments for reforesting/rewilding pasture land, but even if this were done populations of large herbivores still need to be controlled.
One way to do this is reintroduce wolves, which I’m not against, but I still think death by human is the more humane option.
It doesn’t many much sense to me to say it’s bad for humans to kill and eat animals humanely so instead condemn them to be torn apart by wolves!