My boyfriend is a vegetarian and I'm a meat-eater. I was brought up eating meat and his family was brought up vegetarian.
He's perfectly fine with me ripping apart a Nando's chicken in front of him or with me cooking bacon, but he occasionally has to cut up meat and cook meat as part of his job so I think he's just used to it but prefers to eat vegetarian. And I've tried loads of really wonderful, healthy new veggie food when I cook for both of us that I wouldn't have otherwise discovered.
However it'd bother me if the other person had a superior attitude about it, for example constantly asking me why I couldn't kill a chicken myself, or making sad moo-ing noises every time I eat a cheeseburger. It's just a choice and not something you should shame someone for just because they don't eat the same way you do.