As a vegetarian on ethical grounds (mostly due to factory farming of meat) I politely disagree with your assessment.
I have to decline and explain in social settings all the time, because I will not eat meat served to me. But I do not need to preach when I observe others eating meat. I, like all humans, have a finite amount of time and energy. I'd rather spend that time focused on where I think it will do the greatest good. And that's rarely explaining why factory farming of meat is truly evil.
The best time is when someone asks, "why don't you eat meat?" Then you can have a conversation. Otherwise I've found it best to just quietly and politely decline, as more often than not one can be accommodated easily. (Very occasionally, though, someone feels it necessary to try and score imaginary points on you because they have some axe to grind against vegetarians and vegans. I've found it best to let them burn themselves out and move on. Life's too short to worry about them.)
it's not just a dietary choice and it's a personal lifestyle in the sense of it being your choice, but not in the sense of a lifestyle which is limited to your private space.
You think it's wrong abusing animals. Why would you relate that only to you and think it would be ok for others to abuse them? You wouldn't
Frankly, I more often see meat eaters get defensive. We got to a restaurant, the vegan guy gets a meatless meal. The vegan guy gets bombarded with "Oh, you don't eat meat?" "Why?" "What's wrong with eating meat?" "I just like having a steak now and then."
