Unfortunately yes. Plant products required to replace micro-nutrients and aminoacids from meat would produce enormous carbon footprint themselves. Veggies simply compare eating meat with eating grass, or at best eating corn and grain.
Not even starting to introduce finer points, which average veggie finds too difficult to understand. Most land used for raising livestock is impossible to convert to productive cultivation. The land used for extensive ranching of livestock for meat cattle - the least productive kind - is often the best habitat for wildlife, precisely because most carbon is unused by livestock so can nurtue wildlife.
You seem to be very convinced of what you say, and bring up some "finer points, which average veggie finds too difficult to understand".
Let me first get this straight after coughing up a master thesis in soil chemistry, having had courses on topics including climatology, animal and crop production, soil degradation and land use as an environmental engineer:
a vegetarian diet will reduce carbon emissions significantly, yes. There is no question about it and if desired, I will link to various studies. If you find information in the opposite way, I invite you to share.
As you mentioned the shortcomings of a vegetarian diet in terms of missing micro-nutrients and amino acids: a vegetarian diet is balanced and healthy for most people without any need for compensating with food supplements.
I eat vegetarian for the last 6-7 years and I don't feel I am missing anything (my 2 kids are 3 and 5 and have never eaten meat, and they are super healthy). I happen to be a competitive cyclist and have won races. If that doesn't prove it can be done, I don't know what else to say. I won't say it will work for everyone. Some people won't take up enough essential nutrients with a vegetarian diet, but the same can be said for certain people that don't easily tolerate meat in their diets. That is something very personal.
It can more easily happen you miss out on essential nutrients and vitamins, especially if you would go full vegan (no animal products), I would think some nutrients are hard to get into your diet and have to be taken e.g. as pills, which is not what I would describe as a balanced diet, and not something I am aiming for personally.
Anyway, the message is that many 100ths of millions of Indians, and maybe already more Westerners prove on a daily basis that you don't need meat to stay healthy. If you want the message more pragmatically: just eat half as much meat and you won't miss your meat, but you will be as fine.
Next is the question if meat production is bad for the environment (and CO2 emissions). Well, another firm yes. Land used for raising livestock is indeed, at least historically and in the poorer parts of this world, for a great part, land that cannot be used for crop production.
But you are missing some context here: a lot of the land that is currently being converted for livestock (and has been converted), because of the growing demand for meat, was either forest or is currently being used for growing animal food crops (like soy and maize).
In other words: we use land perfectly suited for human food production, for animal food production. By feeding animals, most of the energy stored in that food is converted into heat (respiration, maintenance of the animal's body) and only a tiny part goes into the actual growth of the animal. I am not even talking about the fact that you need more than 1000 liters of fresh water to produce one 1kg of cow meat. The main message is that meat production is a very ineffective way of using the land in order to feed humans.
I has been calculated that all humans could be perfectly fed on 1/5th of the current agricultural land surface if we would go vegetarian (i.e. not even vegan). That means that 4/5th of the current agricultural surface could be converted into whatever was the original vegetation: forest, wetlands, grasland,...Just think about that: not eating meat would save the whole of the Amazon and much more.
And it's not only about forests: permanent grasslands capture quite a huge amount of CO2, and if that grassland is being plowed to grow maize for animal food (like is happening all over Europe), a lot of CO2 is released from the soil organic material.
Yes you can have good land use by e.g. grazing cattle in the vast open prairies of the American prairies. You better wouldn't use those prairies for something else. But even that 'ideal' image has its limits: more and more parts of the world are severely overgrazed. e.g. many African savannah parks experience daily clashes between the wild animals and the big herds of cattle farmers intruding. Overgrazing is threatening birds like Great Indian Bustard, Liben Lark, Jankovski's bunting and many more with extinction.
Instead of attacking a group of people for their behavior in a quite denigrating way, I invite you to come with arguments.