Someone who obnoxiously promotes their personal eating habits. Can be compared to religious fundamentalists.
Mad cow? shit...the militant vegetarians will be dancing in the streets.
A vegetarian, who is not content with others eating meat around him/her. May try to influence there 'traditional' ways with photos of mutilated animals and moan when his/her things are used in conjunction with meat products.
1) "Goddammit, that Katherine is a militant vegetarian"
2) Militant vegetarians should be burned at the stake, over a pile of foot and mouth infested cattle