The more 'efficient' farming strategies are frequently more stressful for the animals, with higher yields requiring more intensive methods, so that must also be balanced, though I am more than willing to accept your thoughts on both the petrochemical business and Joachim Phoenix. (To an extent. I'll come onto that.)
Also good to remember that meat is frequently transported and stored chilled, which again has an impact which is different to other forms of protein such as pulses.
I have read the figures, but I would say to you, why NOT meat? Most of us already try to avoid flying, packaging, and are careful with our buying habits, and no one seems to have quite the same emotional reaction to those things as they do when asked not to eat meat. I don't understand why. We already do the other stuff and a 'look over there!' attitude is not helpful.
Celebrity hypocrites. Okay, this annoys me. As soon as a celebrity sings the praises of good environmental habits, the press will immediately try to find something they did that was not good. This means that the message about the good environmental habit, from someone who could actually have a positive impact, is lost. And it's become absolutely routine now. 'Take that, Greta! Not so squeaky clean now, are you?!' we just can't help ourselves.
My point is that food overall is responsible for 10% or less of overall emissions in developed countries, and if you were going to "spend" carbon on anything, keeping people fed is probably more worthwhile than a lot of the other stuff. Cropping is also responsible for emissions, so why single out meat?
My other point is that certain systems that produce meat help to sequester carbon - grazing livestock systems.
People do not avoid packaging - look in a supermarket, everything save one or two loose veg are packaged. It's bonkers. People certainly don't avoid pre-prepared foods which have loads more transport and industry involved. People do not appear to be avoiding flying either- look at the clamour for travel whenever restrictions have been eased a bit.
This is because people are sold a vastly overestimated impact of meat as a whole and think that somehow because they don't eat it, this might go some way towards mitigating taking a massive fucking plane all over the place - which is why I used Joachim as an example.
As I've said before, climate friendly diets will vary with locality - if you live in the UK, we are fucking good at growing grass, thanks to our climate, but pretty piss poor at growing milling wheat. Soya is starting to come out of some animal diets (as it should, none of the animals we farm need soy, we grew them perfectly well for thousands of years without it) - for example M&S won't allow soy in cattle feed for their dairy products (the farm at work now supplies them). Veg production here is problematic because it is often done in a way that adds to soil loss (which is the real issue, it is ultimately the soil microbes who sequester most of the carbon)
I am not saying that farming and especially not the food supply chain should change, it is an applied science and as science changes, so should it.
To me, the most sustainable diets are local ones. However, the supermarkets have made this very difficult. Local abattoirs are closing (and either way, they use central collecting points for all things which adds a huge number of miles and therefore fuel), there are numerous incidences of misleading packaging (union jacks on products imported and simply packed in the UK).
Cropping and livestock are integrated systems and rely on each other.
There are some things which could help and I consider them to be things like:
Regenerative ag (which will involve more animals on arable farms to bring fert by grazing in rotation with no transportation costs whatsoever) which may lead to some destocking of the marginal upland areas (there is an argument about cultures being removed if you do this and I hear it a lot from Welsh and Scottish hill farmers, the latter of whom seem to see it as an extension of the highland clearances, but that is a different topic).
A completely new look at pig and poultry (which provide 80% of the meat we eat anyway) - both of those creatures were originally domesticated to exist in small groups alongside humans and make use of scraps. There are some really interesting systems putting meat birds on ground after combining to eat the spilled wheat (which can run into the tons, by the way). Which, ironically used to happen post war, so nothing is new. Rather than centralising these things in numbers they should be more spread out (as it were), both have an important function in minimising waste.
Urban farming - I've read a few papers on this now and it does seem to have numerous benefits, often more efficient than mechanised horticulture (you can grow up as well as out because harvesting is done by hand), community benefits (social cohesion is mentioned in numerous studies).
Cutting down on waste - to me this is one of the biggest issues in food at the moment, and I don't think the responsibility lies with the consumer as much as we are led to believe, supermarkets should be penalised for food waste and that which is wasted and not suitable for feed (foot and mouth put paid to a lot of food recycling through animals - it is now illegal to feed any livestock anything which has been through a kitchen) . There are promising projects using food waste to grow soldier fly larvae (which are massively efficient) as a protein source (for inclusion in feed) which would make loads of sense for, say poultry which naturally eat a lot of invertebrates anyway if you let them.
