Staying vegetarian is easy enough because it didn't take long before the concept of consuming animal flesh started to repulse me. Even after about 6 years I still feel occasional impulses, probably because I grew up on southern BBQ, but it's really small and easy to pass.
So here's what I will say about this. Not everyone's dietary choices are rooted in ignorance. Everyone has different bodies; different hormones and chemistry; different synapses. All we can ask is for everyone to try eating mindfully at minimum. That alone is a great start and will make a huge impact.
As for how we feed our pets, I agree with this article, and I'll add pets have such short lifespans, and very few needs, the least we can do is try to give them the highest quality version of the few needs they have. For better or for worse, my cat is a spoiled princess because of this.