Veganism is not private. I think to understand this statement we need to first explore why people are vegan, and then use that knowledge to figure out how we can best act to suit the needs of the vegan social movement.
I think all vegans should be able to answer the one simple question, 'why are you vegan?' It is something, I feel, we are required to answer and should expect to be asked. When I first became vegetarian once upon a time my answer was because I don't want to contribute, in any way, to the possible suffering of an animal. I went vegan the day that I learned that vegetarians still contribute to suffering. Since I didn't know any vegans at the time why I became vegan was something I thought I knew – but didn't really explore. To me I was vegan because I didn't want to hurt animals. Sometimes it was because I wanted to save animals. Statements like that open up a lot of questions. Who am I being vegan for? Am I really altruistic, or do I just want the attention of others who praise me for my noble choices? Would I be vegan if it was harder, or if I wasn't really saving anyone?
A friend once told me a good story. Perhaps it's a well known vegan story, or maybe he just made it up. I can't quite say. He said to me when people go vegan we aren't really saving anyone. It's not like at the slaughter house they keep a tally of vegans and every time someone goes vegan they release the right amount of cows, sheep and so forth. So if we're not really saving any tangible physical real non-human animal, why are we vegan?
I do think we are eliminating non-human animal suffering, but with theoretical other animals. Veganism is not just a diet. The diet of one vegan isn't very useful in isolation. If we imagine we are voting with our wallet, as the film Food Inc. suggests we should, I think we can get a better picture of why we are vegan. I am vegan because one day I want animal (non-human and human alike, which don't fool yourself still exists) slavery to end, and to get there we need to change the system. It needs to not make sense for people to have slaughter houses and wear cows. To do that we need a change of consumers from omnivore to vegan. When what you are buying changes what people will produce changes. I am vegan in the hopes that if I continue at this one day farms won't exist anymore, they will be a horrific relic of a past humanity is ashamed of. I am saving hypothetical non-human animals from suffering, the ones that have not been born yet.
It's important to realize that real structural change does not have an easy quick fix. So, by being a private vegan and sitting in your corner and not talking about veganism – you're not really helping. You are not saving physical real non-human animals now (because veganism doesn't do that) and you're not saving theoretical non-human animals in the future. If everyone was vegan you'd be doing a great job, but that's not the case. As an isolated vegan your vote is just one vote, but as a vegan that lives a vegan lifestyle you can influence the votes of others.
The idea is a little dismal at first, that what I am doing (no matter how hard I try) is not saving anyone today. It's not even saving anyone that I will ever know, will ever exist, or of course can ever say thank you. I think sitting with that idea for a while is acceptable, but then we need to make a new definition for ourselves of why we are vegan. One that fits the goal that we actually need to have. I am vegan because suffering is unacceptable. Animal (non-human and human) suffering is built into how our society functions, it is often ignored because other animals are not equal to humans, and I will do anything in my power to change that in a permanent way.
I like to think a vegan lifestyle as a road to non-violence. You start wherever you can and work towards the end goal of reducing suffering as much as physically possible. If you are always moving towards that end goal and making practical and responsible choices to get there, then where you are right now isn't the most important. So yes, being a private vegan is acceptable if that's where you are right now, but to think that being a private vegan is the end goal is a big mistake. Living vegan starts with your food, and then it begins to emanate from you. It is present in your morals (ending suffering peacefully whenever possible) and becomes a way of life. People that talk to you can see your vegan-ness, and choosing not to hide it and to say I am this way because I am vegan is very important.
So to all the vegans that sit quietly at dinner tables and don't speak up because it would be impolite or awkward to do so – I hope that's only one step on your path and you don't always plan to allow suffering to pass in silence.