Welcome to permies! think it's great how you've jumped in and started participating and making this place your home.
You've asked a great question and it's SO nuanced it's hard to answer without writing a book (and in fact people DO write books on this topic). This is just my attempt to briefly answer your question based on my experience.
I think most people agree that animals are capable of feeling and thinking, but for lots of different reasons, most eat them anyway. In my later years of being an omnivore, I focused on eating items labeled as free range, humanely treated, organic, etc. (I've learned since that most of those labels are essentially meaningless as far as the way animals are treated or whether they died in fear and pain.) When I ate animals and their products, I enjoyed the taste, but mostly did so because I believed it was necessary for my health. Essentially I was choosing me over them. I think a lot of people are in that place.
I stopped eating any animal products except honey almost six years ago. I made that decision, after a lot of research, for health reasons. My health is better than it's ever been even though I'm almost 50, so it was the right decision for me. The fact that I'm not directly causing animals pain and death adds to my overall joy and peace, especially when I see documentaries about how conventional animals are treated. Or during those times when I start thinking about something higher up the food chain caging, killing and/or eating me the way many of us do animals.
From my experience with permaculture people who participate in animal eating, there is knowledge that something with feelings died and there is appreciation and reverence for that life. There is belief that eating animal/products is healthier (at least for them). There is consideration that small-scale, local, personal animal raising and eating is less harmful to animals as a whole than things like clearing land for large-scale farming would be. Practically, it is definitely harder to raise / grow all your calories if animals aren't part of the equation and a lot of people here really care about self-sufficiency.
Ultimately, I feel guilt is a wasted, harmful emotion. I think it makes sense to keep evaluating if one's diet and way of life works for them. I think if someone is living life well, they are passionate about things. It sounds like your son is passionate about veganism and that might be a temporary or lifelong state. I don't think it's possible to live life perfectly, to truly harm no one and nothing. I think we all need to choose how we spend our energy and our passion. It sounds like you and are your son are both sincere, loving people and you're currently passionate about overlapping but different things. That's not a bad thing. And there's a place for you on permies regardless of where you fall on the diet spectrum.