Hello Lisa.
I'm a vegetarian (for 39 years) but couldn't make the leap to veganism, although I know I should.
Anyway, I think the hostility to us who shun meat-eating is about guilt.
Meat eaters KNOW they're in the wrong. They know that as individuals they simply couldn't go out and kill a chicken, a pig, a calf, probably not 'even' a cod or a tuna, in order to eat it. They can only carry on eating dead animals if someone else does it for them.
And they feel guilty! And therefore take it out on us, who (while failing) are at least trying to live lives based on more humane principles.
BillB