I'm not going to go point by point because I think it's not productive to act as if this kind of argument has only two sides. When we talk about subjects in a persuasive fashion, where we're trying to win someone over to our side, it frequently has the opposite effect, entrenching is into our already polarized views.
We need to concern ourselves with moral relativism to make appropriate decisions. In an ethical sense, I believe sexual assault of a human is at least an order of magnitude worse than milking a cow. But that opinion comes largely from the fact that I'm a human and I'm not a cow.
If we want to sway someone's opinion, I think we should focus less on absolutes and more on quantities. We should meet people where they are. Maybe instead of driving home all the disturbingly true reasons we should never milk or even breed cattle, we should use those same arguments to highlight the absurdly destructive impact of doing those things at the scale which we are.
If half of society has a burger and a milkshake once a month, there is a significant environmental impact on milking those cows and raising those cattle to be slaughtered, as well as a very real moral cost. There is also some emotional benefit to the human of consuming fats and proteins from those sources. And both positive and negative nutritional effects as well.
It's already difficult to compare costs and benefits from such wildly different categories when it's just one burger a month. Humans are emotional beings and even a well-reasoned argument may not trump the emotional feeling one gets from a hamburger and a shake.
But consider the changing of factors if those same people go from one beef product and one dairy product a month to one every other day. Or even more frequent. How much more land it takes, how much more suffering the livestock go through in conditions designed for maximum profit and minimum concern for moral costs. The additional methane production, the deforestation, the added risk of heart attacks. All the bad parts multiplied wholesale, while the good parts all experience diminishing returns.
If you take one of those semi-daily beef and dairy consumers, and give them a hard line, where any consumption of beef or dairy is unacceptable, is that going to generate a positive or a negative effect on the system as a whole? Some may be convinced to quit consuming, but I feel their difference will be swallowed by those who feel called out in such a way that they would rather consume even more out of principle than face the hard truth that their lifestyle is wrong. It's easy for humans to build walls of cognitive dissonance, where we know what we're doing is harmful, but we make excuses for ourselves to avoid facing that reality.
If you want the masses to face their collective reality, we need to meet people where they are. Maybe burgers and milkshakes will always be part of your life. But there are alternatives that can be a different part of a life rich in variety. If someone currently eats a burger every other day, maybe they can strive for once a week. And if that goes well, once a month. And then, once they have a greater familiarity with the culinary variety that's possible, they may start to forget to eat that meal entirely.
We should remember that we're all just people. We don't need to be on different sides. You don't need to be wrong and neither do I. We're just earthly passengers connecting electronically in a wide cosmos. Our lives are all so different and yet uncannily familiar. So we'll get more mileage out of sharing our experiences than prescribing them to others. Because if we feel we're being talked down to, we'll decide we've already picked a side. But if we're just sharing, then we're all on the same endless side. In that spirit, none of what I'm saying is meant to invalidate anything you've said. Only add to it.
And just to add, I don't mind if there's a bit of feces in my milk. It looks perfectly white, so I imagine it's in low enough quantity that it's not a health risk after pasteurization, and as far as I know, the quantity is also low enough that it doesn't effect taste. But I think cows should have good lives even at the expense of productivity, and milking should be a voluntary behavior, perhaps in exchange for appropriate compensation, rather than something that's forced on them. Just my two cents (plus about a buck fifty).