Well, the next time you will be better prepared just from this experience. You might also want to prepare a little bit now while it's fresh in your mind. *
From my own experience (and without any evidence) is that many of the people who question you are legitimately curious and/or concerned for your well being. Perhaps their biases and ignorance might frame the question awkwardly or even antagonistically. My advice to accept each question in the best light and then give a short polite informative answer. The answer doesn't need to be complete. if they have other questions you now have a conversation.
If you did go vegan for animal rights, I wouldn't shy away from that. I think it's something to be proud of.
Keep in mind that although we may have heard the question, "Where do you get your protein from?", like a million times. It may be the first time That person has asked it. So give them a good answer. "Beans, seeds, and nuts." is pretty concise.
Never miss an opportunity to befriend or educate.
*If you're like me you will rerun this in your mind like a hundred times at 2 AM. But I don't recomend that as a strategy.
Have had similar conversations in one on one interactions. My brain can better recall information without being pressured by a whole group of subtly irritated/defensive family members.
There are so many strategies to lessen the defensiveness of people who are resistant to talk about being vegan specifically.
One thing I try to remember is that saying you are "plant-based" instead of the word "Vegan" can loosen the image people think of when they assume what a vegan is and how there tends to be an emotional charge attached.
Another thing to bring up is my personal connection to working in sushi and being exposed to visible worms, parasites, and methyl-mercury exposure over many years. That when I increased my fiber intake it did wonders to help my gut recover from the abuse.
Not to forget that at the time I didn't want to be directly contributing to the overfishing and extinctions to certain types of Tuna.
Also important to bring up leaders and celebrities that other people respect who they might never guess have adopted a plant based diet. Arnold is one of the biggest examples of someone who has reduced their meat consumption and moved towards being Vegetarian.
Being that my family is mostly liberal and Jewish I could mention also that John Stewart and his wife have moved to Vegan diets and talk about the impact of factory farm meat industry.
For the protein argument I usually ask about how people think that Gorillas get such large and powerful muscles. Most people will struggle to find the answer to which you can say that these primates are primarily grazing on leaves as well as fruit and 2% or less being from bugs..
Another point to bring up is that I get 100% of my recommended daily value in all of the 9 essential amino acids. That these are abundantly found in the plant kingdom.
It's better to feel out what the other person is resistant to listen to and in a way back off from pressuring them or trying to flood them with your side. Instead people will let their guard down if you present the information in the form of telling a story rather than trying to let them know how you think they are wrong in any way. Instead that this is a more a factor of moving towards a positive direction in my own life.
Bringing up that you are in some way against their choices or that they are directly contributing to the suffering of animals is not a great first conversation to have.
I could instead mention an experience of when I was trail running in high school and ran into a mother and her baby sitting right in front of me. That I locked eyes with the mom and had a spiritual connection. That they somehow realized I was not a threat and it was apparent to me that they were having a unique experience of their own.
The list goes on and on. As the conversations become easier it will help in remembering these things in the moment and shine a light on how this relates to personal growth. Finding ways to first remove the defenses of the other person through story telling and then sneaking in some of the deeper truths.
