While not easy to do, or think of when a person gets upset. If you are in that situation again, I would politely answer your mom, ignoring the little @$$$ affirming her question, then directly thank your host/hostess. He is seeking the attention, from what i would bet the host/hostess made a fuss to make sure you were comfortable, and he didn't like that, plus if you already don't get along.. .that makes it worse. Now saying that ... as a teenager, I would have probably dropped an F bomb or 2 and told him to go suck out the rotted meat between his teeth before he contacted mad cow.
Anyway those types of things get easier.
I forgot who posted about the friend that always makes a big deal out of you being a vegetarian, don't read to much into it... she obviously cares, just doesn't know how to deal with it. I will give you a humorous example.... My 6 year old is in Barnes and noble with me the day after Christmas, in the center of the store was a huge book display, with none other than Skinny *****.... My daughter Yells.... "HEY MOM, THERE'S SKINNY ***** ARE YOU GOING TO GET ANOTHER COPY SINCE YOU GAVE SHELBY YOUR COPY!"...... crickets in that entire store.... my son was walking away rather quickly... "I responded, not now sweetie... let's get your books today.." and went on... point is people who care will embarrass you or make you angry in some cases, but they want you to know they accept you, and want your acceptance....