This is the problem though. Too many people consider the very existence of vegans as a comment on their morals. If you ask a vegan why they refuse to eat animals, they will almost always say that it's because they believe it's wrong to kill animals for food when there are alternatives available. By definition, they are therefore saying that you, by eating meat, are doing something wrong in their opinion. You have basically given them impossible conditions for their choice. What you're essentially saying is that it's fine to be a vegan as long as you're either doing so for no reason, or at least lie about the reasons if asked and never bring it up in conversation. I've known a lot of vegetarians and vegans in my life, and I've only ever known one who was an arsehole about it and actually made a point of making the moral argument whenever they saw someone eating meat (ironically a vegetarian, not a vegan). I've met far more people who see the very existence of vegetarians or vegans to be a personal affront to their morals and feel the need to challenge them on their choice of diet when it comes up. They're like the sort of people who upon learning that someone's a Christian say, "Oh, so you think we're all going to hell then, do you?"