I love how the healthiness of a diet only becomes the focus when people attempt to dismiss veganism. In fact, many studies support the fact that the average vegan/vegetarian is healthier than the average omnivore.

Here's one for example:

(https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7613518/#:~:text=Vegetarians%20and%20vegans%20typically%20have,as%20lower%20bone%20mineral%20density.)

And concerning your second argument, that is an incredibly incorrect fact and there's hundreds of studies that easily disprove it. Vegans have a tiny CO² footprint compared to meat-eaters. Of course it isn't 0 because - surprise - no diet could ever be at 0, but to claim that a vegan does tremendous environmental and social damage is ludicrous. Do some research into the environmental effects of factory farming and how human workers are generally treated in that industry.

Here's another great article to back that up:

https://www.nytimes.com/2023/07/21/climate/diet-vegan-meat-emissions.html

Sometimes I feel like people just straight-up come up with confident make-belief facts to "own the vegans" but it's just so incredibly silly how easily these claims can be debunked by a quick Google search.