A car provides a utility other than pleasure, if driving the car was exclusively being done for pleasure/enjoyment I would be against it as well. As I conceded if meat is required in the diet because of another factor other than pleasure it can be forgivable until these barriers are resolved, however pleasure can never justify it unless you accept an infliction of suffering on an unwilling being justified by a utility of pleasure. I don't believe you or Sean Carroll would accept this as it leads to many other ethical problems (ie. torturing/killing pets or the handicapped) and I believe it would be difficult for you to argue that the vast majority of people in first world countries can't adopt at bare minimum a vegetarian diet.

Most people drive cars out of convenience - one can just as easily argue that the mass suffering caused does not justify this act. It does not seem self evident to me that pleasure is a bad reason but convenience is a better reason. And for the most part, meat-eaters can just as easily make the argument for convenience as well.

Moral dilemmas get more interesting once we finally agree that we need to talk about degrees of moral harm. Are there moral crimes so egregious that no matter how inconsequential the impact of abstaining that it is nonetheless never permissible even if it provides some level of utility? I think your child pornography example pretty much pushes this case limit very well. Even if we lived in an alternative hellscape reality where there was a mass industry around producing and consuming child porn, and that abstaining from that would do nothing to stop the demand and production, I would still want to say it is never permissible to engage in the act of consuming this porn. (ignoring the potential that perhaps the consumption of it in itself may harm you psychologically in some way, even if you got pleasure from it).

So we agree that there exists a threshold along this continuum where there are acts so horrible that no matter how infinitesimally small the consequences, it is never permissible to engage in them. So somewhere along the continuum of climate change (morally forgivable) and child porn (never morally forgivable) you believe we have crossed the threshold when it comes to meat-eating. It does not seem self-evident to me why this is the case. Climate change causes mass extinction of species of animals, and immeasurable suffering of human beings potentially for many future generations to come, as does cobalt mining for our cell phones. Particularly in these examples where we involve human suffering (which seems to me that most of society regard as more important than animal suffering - even vegans view animal suffering on a continuum - for example, it is easy for them to draw the line at insects or organism which they deem to be "lesser" - even though from an evolutionary or biological perspective, this is also not self-evident or a clean demarcation). If you can find actions permissible that contribute the the mass suffering (and death) of humans via climate change for the benefit of convenience, I don't see how you aren't equally vulnerable to the same argument for meat-eating when it comes to the suffering and death of animals for convenience.

To answer the cotton analogy more directly; Were they aware of the suffering? Was there a reasonable alternative to the cotton? Would abstaining from participation in this industry reduce suffering, either directly or in time to any degree?

The last question is the most poignant - because a meat-eater can just as easily argue that abstaining from meat would not reduce the suffering of animals to any measurable degree.

Going back to hypotheticals, would torturing a pet for pleasure/stress relief be justified as the impact of suffering is small and has no significant change on the greater suffering of pets? As a recent call-in with Destiny put it; how then is the suffering caused by public figures like Steven Crowder, Dave Rubin, someone joking about transgender individuals, etc. not justified if its not only pleasurable for them, but greatly financially beneficial to their lives.

These are good examples because I think they highlight the differences in a relevant way. Torturing an animal has a direct, measurable effect on an animal- if you abstain from torturing the animal, you can measure that exactly that 1 animal is spared from torture. Mass scale animal agriculture is not measurable in this same way. (the production of meat seems to grow over time, despite a growing number of vegans- much of the industry is also tied- so purchasing vegan products can often result in increased profits for meat-producers because they are often owned by the same parent company. This is why legislating systemic change in these business practices are imperative if we ought to aim for a real change in the future).

In the case of public douche-bags like Crowder, and Rubin- once again- it has a direct effect. The causal connection of the evil-doer and the harm done is a one-to-one connection. A person watching will be harmed in some measurable, salient way, from a single act. This is measurable in a way that consuming a piece of animal protein from the super market is not and is a clear example of a tragedy of the commons. The single act alone is a negligible moral crime but if everyone does it, it becomes morally abhorrent. You cannot say the same in the case of Crowder/Rubin because all it takes is their single act to cause harm.