The idea that you are not causing any harm because the meat is already on the shelf completely ignors basic economics of supply. This is exactly the same as saying that it doesn't matter if you buy clothing made in a sweat shop with abused little kids working 16 hours a day? But, that does not matter because the clothes are already on the shel? That's nonsensical! Do you think it's ok to buy clothing made by abused little kids? Most people think that's not ok!
Of course it has to do with emotion. That's what's is all about to begin with. The emotion is compassion.
When I said emotion, I meant afflictive emotion. Real compassion also includes everyone in the whole samsaric network.. those who are currently "victims" and those who may be inflicting suffering, since they're just one step from the other side of the equation. Anyway for the sake of examination we are trying to locate who is causing suffering here, regardless.
You are bold to bring up sweatshops, since you are on a computer now clearly, and therefore making use of one of the most abusive industries. Are you willing to abstain from computers, laptops, and smartphones?
Back to the OP, I think the point is the basic math of industrial agriculture, meat production, and how much is wasted daily , i.e. thrown away outright. This is all discussed ad infinitum earlier in this thread. A few Vajrayana Buddhists in the USA are not going to shift the supply and demand networks of this industry. I do believe it is important for large monasteries in India for example to be vigilant about this, because 1000's of monks ordering meat on a daily basis is going to certainly affect supply and demand on a local level.. clearly this was a hypocritical reality of Tibetan monastic institutions. And it is significant that the Dalai Lama and the 17th Karmapa have eliminated meat in most of their monasteries.
Anyway, I see both sides, to the point that I could argue both. But I won't argue both.. I don't think it should be an argument at all but a personal choice based on what you feel is correct.. not trying to convince another practitioner that their choice is wrong. That's the bottom line. I think it's great if some people here choose to be vegetarian and can stay healthy that way. That's been my path.
I also think it's great if some people here feel they need to eat meat for their health, and have been given tools to try and create a compassionate and beneficial relationship with that animal they might eat a part of-- through mantra practice, interdependent inevitability, and whatever else.
I don't have much respect for those who thoughtlessly eat meat however, without compassion and respect, and without remorse for the savagery of the industry.