Making a conscious decision to go against biology and select a different dietary preference is indeed an ideology (unless there is a real medical reason you cannot eat something, such as allergies).
First, nobody said anything about eating only meat as a diet. I'd wager zero people do that - you would quickly develop vitamin deficiencies and ultimately fall ill and die.
Secondly, you've moved the goal posts to vegetarianism, which is not veganism.
Third, just because a vegetarian diet can be sustainable (in the sense you won't fall ill) doesn't mean it's the natural diet for a human. It's not... Your teeth and many other parts of your human body tell us differently.
Fourth, there are several cultures on this planet that strongly favor vegetarianism, but none are strictly vegan and few are strictly vegetarian. As already pointed out, vegans often have to take supplements to remain healthy. That's biology telling you that diet isn't natural.
Lastly, deciding to be a vegan because you believe current agriculture practices are harmful to the environment is a choice based off your beliefs and therefore is an ideology. That was the original assertion.
Veganism is a subset of vegetarianism. I'm trying to be flexible with my position to allow for good discussion - being either vegetarian or vegan is typically healthier and objectively better for the environment [4].
Recognizing that humans are omnivores also means that by definition we can sustain ourselves solely by plant or animal matter [1]. Your statement of "Making a conscious decision to go against biology [...]" is plainly inaccurate, as we are quite capable of living healthy lives without meat.
There is plenty of evidence to support the fact that animal agriculture is harmful to the environment [2][3]. In fact, it is the second largest contributor of green house gasses.
I get the sense that there is some frustration coming through in your thoughts. Please keep in mind this is exactly how cognitive dissonance expresses itself. Take a breath, check out some of the citations below, and try to think about this data with an objective approach.
0. https://en.wikipedia.org/wiki/Carnism
1. https://en.wikipedia.org/wiki/Omnivore
2. https://ehp.niehs.nih.gov/doi/full/10.1289/ehp.11034
3. https://climatenexus.org/climate-issues/food/animal-agricult...
I am genuinely curious to know why you say that. The other poster didn't say anything about not eathing fruit and vegetables etc. They said:
=> Making a conscious decision to go against biology and select a different dietary preference is indeed an ideology (unless there is a real medical reason you cannot eat something, such as allergies).
I can't see where in that comment the OP said or implied that it "goes against our biology" to eat fruit and veg etc. It's clear to me that what they said goes "against biology" is not eating any meat. That is what characterises the vegan diet: the absence of meat and animal products, not the presence of fruit and vegetables.
So why did you say that eating fruit etc doesn't go against biology? Who said it does?
Did the OP change their comment between the time you replied to it and the time I read your comments?
Let me know if you have any other questions!
0. https://en.wikipedia.org/wiki/Omnivore
Edit - actually, sorry, but please don't. I remember interacting with you on previous topics about vegetarianism, and your comment history and name are indicative of some biases and dissonance that you're unwilling to overcome. Even some of your submissions are heavily biased, dated, and subsequently refuted [1][2]. The evidence supporting my position is plain and well-documented in my other comments. Cheers.
1. https://theconversation.com/ordering-the-vegetarian-meal-the...
2. https://theconversation.com/vegetarians-cause-environmental-...
