I have some questions you probably never considered, and please note that this is not a personal argument directed at you or your beliefs and practices.
How do you ensure that 14-15% of your diet is protein when you're a vegetarian, without hitting excess carbohydrates and fat to attain that percent? This is the required satiation level of protein that we have determined in dietary experiments, as well as observed in traditional diets across most cultures in the world. When that number changes, we observe dietary epidemics, like in the Western World today, where the average meal is now 12% protein, and fast food 10%, which has lead to a long term obesity crisis because of excessive calorie intake in an attempt for our bodies to reach the 15% protein goal.
Before you start quoting beans and soya as a protein source, legumes are a really bad source of protein, not because they have only about 13% protein by mass, but because they have about 65% by mass carbohydrate. Therefore you would see that in order to hit your daily protein goal you would be excessive on the daily carb intake. Thus you would have to use artificially processed sources of protein that requires a lot of energy and wastes the majority of the food source that it is extracted from. Once something is artificially processed, you loose the health benefit argument, because you really have no idea what they add to or do to this food to now make it palatable, or understand the effects such a food will have on the human body long term.
But that's only where the rabbit hole starts. Long term effects to study: what are the consequences of humans not getting the required daily protein intake to function optimally, or what are the consequences to attempting to hit the protein goal on vegetarianism diet? What are the consequences for the lean body mass % for genetically lean people who do not get enough protein?
I certainly know at least, that in human evolution, if we had stuck to foraging the trees instead of learning to hunt, make fire and access bone marrow, we would still be in the trees. The human brain requires a constant and reliable source of energy at all times; it does not rest even while asleep. The brain consumes the most energy compared to any other organ. It would use any source of energy it can find, from simple sugars to complex amino acids and ketones, it doesn't care. We were only able to take that leap in brain evolution when that meat and fat from animals provided the excess energy beyond the required baseline to merely survive. And our brains are what separates us from the other mammals.
So while the morality of vegetarianism is a good and noble argument, morality has nothing to do with how we evolved, or the requirements that humans generally have to be optimally healthy. We are only 72 hours as far away from a reliable food source as
the hunting troupe of chimpanzees in the jungles that hunt monkeys in order to satisfy their protein goal.