I'm unsure what kind of an argument you are making. Consider a parallel that could be uttered in the past:
"Letting women vote has no basis in that there is no precedent."
We know enough about nutrition that we could get all the nutrients needed without animal products. If your concern is about health, then how many examples of vegan people living healthy lives into their 90s would be enough to convince you?
I'm not sure that "women should get to vote" is logically the same as "get your B12 from fortified foods like nutritional yeast and you still end up with B12 deficiency" ...
The main finding of this review is that vegetarians develop B12 depletion or deficiency regardless of demographic characteristics, place of residency, age, or type of vegetarian diet. Vegetarians should thus take preventive measures to ensure adequate intake of this vitamin, including regular consumption of supplements containing B12.
This is solved by a trivial supplement. Millions of vegans/vegetarians take them every day, and many hundreds of millions of livestock (which is how most get their B12, as well). If we didn't supplement our livestock with B12, we'd all always be deficient.
A lot of suffering is avoided with a measly supplement.
In the case of B12, yes. B12 deficiencies are a result of modern farming practices, _not_ plant-based diets. This is why our livestock are supplemented with B12.
B12 was originally sourced naturally by consuming things straight from the ground, like foraging and drinking from streams, or eating animals. Modern farming doesn't allow for a lot of this consuming straight from the wilderness though, so B12 needs to be supplemented. Either into animals so we get it via their meat, or directly, via a supplement.
Your B12 is coming from a supplement either way, though. Vegans just ask that you take out the middleman so that they don't need to die for you to get something that is found in a measly pill.
My response was to parody the statement I was responding to, specifically "Veganism has no solid basis in that there is no precedent." I was hoping replacing just one word would have made the connection as clear as possible. Is having no precedent enough of an argument to stop change? It's absurd on its face.
A) There is plenty of precedent for women being involved in the mechanisms of government
B) Governance is a cultural artefact and diet is a matter of biology. I do not think we perfectly understand culture, but we create it as we go along. The requirements of biology are hard, must be met, and very poorly understood. SO lack of precedent for veganism (plenty for vegetarianism) is an issue
Why fight over a minor problem with my example? If you can't come up with a parallel statement that shows the absurdity of the claim, you're not trying hard enough.
Pick a society that didn't have women voting; imagine someone making the argument "there is no precedent", and notice how it's an absurd argument. It sounds like a conservative's wet dream, implying that whenever there is no precedent for something, it meaningfully counts against that thing. Sure, there is no precedent for surviving a guillotine, but are you saying the intention of my sentence wasn't clear?
How about this, at some point in history someone could have said "there is no precedent for the internet" -- would that have been a meaningful "con" against creating it?
As my follow up question goes: "How many examples of vegan people living healthy lives into their 90s would be enough to convince you?"
A good parallel about veganism is from the past: people were saying "hey, we shouldn't have slaves" and slave owners saying "but I like it this way". To ignore the arguments of the anti-slavery movement by gesturing at some generic concern for well being is absurd. If in fact having no slaves meant that the rich families were going to have less money and would eat less-nutritious food is not a good argument for perpetuating slavery.
"Letting women vote has no basis in that there is no precedent."
We know enough about nutrition that we could get all the nutrients needed without animal products. If your concern is about health, then how many examples of vegan people living healthy lives into their 90s would be enough to convince you?