My ex-girlfriend was a vegetarian, but never talked about it. She was completely non-judgemental - she didn't even bat an eyelid when I ate steak in front of her.
Still, without saying or doing anything, she managed to lure me to the dark side. I miss bacon (god how I miss bacon), but otherwise it's all good, and I'm a happier person because of it.
I don't understand why anyone wouldn't be able to love someone else because of what they eat (unless they eat live kittens or garbage mixed with laxatives)
I also keep my dietary habits quiet*, but occasionally a situation will come up that forces me to admit it (like being at a KFC with some co-workers and being asked why I didn't order anything... and then being lectured on why being a vegetarian is 'unnatural'. It's like they want me to bite into a chicken breast right there, just for kicks. Shows a complete lack of respect IMO. Might also be fuelled by some deep-seated insecurity about killing for food, however minuscule, but TBH I couldn't give a rat's arse as long as they don't get up in my face about it.)
*Because it's nothing to be particularly proud of, and because many people don't understand (and some of them are dicks about it).