In what ways can I share facts and opinions about plant-based diets without appearing pushy and annoying, therefore barring the dissemination of ideas completely?
I am referring here to the popular vegan meme but also to my own experiences of trying to talk about these topics with non-vegetarians.
There is no universal answer to this question, since everyone communicates differently. I can only share some tips that worked for me, and might work for other people.
Avoid introducing yourself to other people, or in a conversation, as a vegan. If people are arguing about meat and how horrible tofu tastes, don't jump in as "Well, I'm vegan and I eat lots of tofu, and it's delicious."
I'm not saying "hide the fact you're a vegan". You shouldn't, since it's not offensive or something to be ashamed of or pitied for. I'm saying "Don't reduce yourself to being a vegan". You're a person first, and a vegan second. When you talk to people, show them that you're an individual, and that veganism is not your defining property.
When I get to know new friends, my dietary choices are not the first thing they learn about me. They'll first get to know me, and later discover that I'm also a vegan. The same thing works on smaller timescales in a conversation.
So, be honest and authentic. People don't want to talk to a sock puppet, they want to talk to a real person. Maybe I'm partially repeating the first point again, but it's important, so let me say it in different words.
When I was a vegetarian, I knew a militant vegan who accused me of not being vegan yet. That's right, accused me. This caused a defiant reaction in me, and I didn't turn vegan until I forgot about him.
Most people don't want to be converted. Noone wants to adopt somebody else's viewpoints.
Corollary: People will start understanding your viewpoints if you give them space to come to your conclusions on their own.
Some people just don't have (as much) empathy with nonhuman animals. And they won't understand your viewpoint. They're not wrong, they just have a different ethics which matches their empathy better. Sad, but true.
Try to understand these people, and make them understand, in turn, that their moral viewpoints are not unique either, and that you have a different viewpoint which isn't irrational either.
Do you know that feeling when somebody is talking to you and you can literally feel the pressure in them to tell you about their opinions and views? Don't be that person. Don't give anyone the feeling that you need to talk about these topics.
Don't frame the discussion such that everyone who isn't a vegan is automatically a Bad Person. Leave room for people to keep face!
Talk about your positive experiences. And by that, I don't mean "talk about your experiences, and frame the in a positive way". No, don't talk about that time when you tried to make seitan and failed miserably as "a great experience". Be honest. Talk about what makes you a happy person. Talk about that time you made a really nice meal. And don't try to sell it like an advertisement. Talk about it because you would talk about anyways.
Don't enforce in-group-out-group thinking. Don't draw lines between vegans and non-vegans. Don't emphasize the differences. Don't point out what food isn't vegan, point out what food is vegan.
Lots of people say something like "I've never eaten a vegan meal before", "It's very hard to prepare a vegan meal" or "There is no vegan food at this place". Debunk these statements lightheartedly (while keeping the previous points in mind i.e. don't jump onto such statements with pressure). Show how a lot of food is just a minor alteration away from being vegan.
I hope some of that helped. If I'm not answering your question well, do drop a comment, and I'll expand.
I always say that I'm a vegan if eating out, meat or animal ethics are mentioned, and I always explain why if asked. Otherwise I never bring up the topic directly. However, I find that I get more than enough challenges and questions from omnivores to be constantly discussing and explaining why I'm a vegan. And I'm an introvert! I don't talk to that many people.
If someone compliments me on my clear skin, apparent health or fitness or general exuberance, I say "I think it's the vegan diet."
Feed people delicious things. Post pictures of the delicious things you are eating on social media. Give cake. In my experience this very often leads to a pleasant (because cake makes everything nice) discussion of why you are veg*n and how great it is (seriously, vegan cake is the best).
We have heard these questions a million times and therefore we should answer them a million times. In one charitable case I sat through my friend's long and detailed line of (stupid!) questions as she eventually concluded "Okay, I think I can pack vegan lunches." That was a huge victory I didn't even know we were leading toward!
Bad: "I can't eat there, there's nothing vegan."
Better: Proactively suggest your favorite Thai or Mexican place before the question comes up.
If a friend invites you somewhere, check the menu and prefer calling the restaurant to drilling your friend about veganism.
Korean BBQ? Don't make a fuss. Don't be gloomy about how you're never invited. You are invited, you are just making dietary choices that are important to you. There will be other times to hang out.
Sometimes it can be hard to say you ate a carrot without being called "preachy." Sometimes I feel people who are that extreme really are kind of being obnoxious. Deal with it however you deal with obnoxious people in extreme cases, but please remember it's not your behavior or what vegans do, it's what they have already decided to believe about vegans
There is a line I will not cross: I am actually doing something that is right and I am generally socializing with people who have not taken the same steps as I am but do I agree I am doing a good thing. When naturally a situation arises when life is more inconvenient because I only eat plants, I define an ethic where my beliefs are respected as much as if I were on a religious diet.
