Okay, so, I don't know how to describe it? It's very much a personal thing, so I don't want it to sound like I'm trying to sway you.
For me, it was when I heard about chickens. How their beaks are ripped out without anesthetic. They are crushed into cages where they can't stand up for move around at all. They're gassed if they don't produce eggs fast enough/or if they can't. And cows! The way they are killed. And fish. They suffocate slowly before they die, and those nets kill a ton more stuff than what the fishermen actually want.
So, this just really...disgusted me? I mean, while reading this I just sat their with my jaw dropped. I couldn't believe it.
I'm still trying to research it and find credible sources for information, so bear with me, lol.
Anyway, after reading this, I just felt like I couldn't participate in it anymore? I couldn't be a consumer of this, because to me, that meant I support it. Thinking about eating a dead cow now, after what I've read, I just can't stomach the idea. I'm not trying to stop an animal from being killed, or convert anyone, or whatever, I just don't feel like I can personally participate in this anymore.
So, I guess it's trying to understand why someone is a certain religious? I'm not comparing vegetarianism with religion or something, but people can't always explain why they do the things they do, or believe in the things they do.