I have to agree with a lot of the other posters in here.
Having others' beliefs - be they religious, ethical, or otherwise - foisted upon me is a pain. While I fully understand vegan beliefs about the sanctity of life, I don't much appreciate it when I'm treated as something less than human for not being a vegan.

Hence why I'm happy that no vegans ever treat me like that
I've got a number of friends who are vegetarian and vegan, for reasons ranging from personal to religious.
Therefore, with the choice being between predator or prey, Vegans, with their refusal to eat anything but plant matter, have taken the option of being prey.
I'd disagree. Being herbivorous doesn't equate to being prey. Eating meat doesn't make one any less suceptible to being eaten, so eating plants doesn't make one less strong and self-determining.
You wrote of the importance of choice - deer don't choose to be prey, they become it.
Vegans choose not to eat animals or animal byproducts, because they feel it is wrong to do so. Not because they want to assume the role of the deer, which has no control over its status; rather, they don't want to benefit directly from the killing of another animal.

I'm reminded of a rather cynical and quite stomach-churning joke from primary school:

"How do you solve all the world's problems?"

"Get the hungry to eat the homeless".