I get it, other people's dietary choices annoy or threaten you. Perhaps you were once inconvenienced by a thoughtless vegetarian houseguest, or you're a former vegan whose health suffered as a result. Maybe you work in marketing for the beef industry and you fear the rise of vegetarianism will cause you to lose your job.
Regardless, there is no good reason to be disrespectful to others for dietary choices that are based on health, moral, philosophical, or spiritual concerns. That includes e.g. vegetarianism or veganism, kosher or halal, or gluten- or lactose-free diets.
If someone's attacking you for eating something that person doesn't eat, then sure, respond in defense of your choice (and a cursory look at Serious Eats comments will show that's a rare occurrence). But pre-emptive strikes about how vegetarianism is simply "trendy" or vegans don't eat "real food" are just offensive, and only serve as hindrances to the sense of community Serious Eats strives to create.