You're saying "vegans" as if we're a monolith. I'm sure there are vegans who aren't aware that plants are considered living, but I'm sure there's about the same percentage of meat eaters who aren't either. If every vegan you've ever talked to (or some, since you've made both claims) has this misconception, I'm willing to bet your sample size is extremely small, or you're being intentionally dishonest to support your initial claim.