As an example, I was in Florida a few months ago and my girlfriend and I casually mention that we were making a salad for dinner after someone asked about our dinner plans. Their immediate response was defensive, saying, "Are you one of them vegans? Well, we only eat meat around these parts" and proceeded to tell us all about these great deals on meat at a local store, thinking that we'd hear those prices and be unable to resist and start eating meat.
Just because we mentioned a salad, his manufactured, mass-produced opinion was that we must be vegan. We're not. She's vegetarian, I'm pescatarion, but the difference is immaterial to a meat addict who's been sold a crusade.
It's the same story with our country's cult-like addiction to alcohol. Every time I go out and don't drink, I have to explain to people that I'm not a teetotaler, and have to explain the foreign concept of moderation. They get defensive and try to get me to drink anyway, because if I don't, they're forced to reckon with their own lifestyle choices of excess. Exact same issue with our meat consumption.