Right, so just so we're clear- Tom is a celiac and a doctor ordered vegan, who can't control what food goes in his mouth, so therefore everyone he knows must also become gluten free vegans? That just screams SS.
I am celiac, I cannot cheat, I get too sick. I used to be vegan, and to require a 16 egg recipe cake be changed because I won't eat it (and it isn't my birthday!) is beyond SS.
Furthermore, I would never EVER require anyone to make something GF "just" for me. I go to events knowing that I will not be able to partake, and will leave the room while said dessert is being served so people don't notice that I did not have a piece. If someone does notice and ask, I simply say that I'm sorry, I can't have it, but it does look delicious. (And yes, I too have gone into hysterics from pure hunger and need for cake. Never for long, and only in private, but it has happened. I think it is called "Hangry". There are some really good GF cakes, and even vegan ones, but you can't just modify any recipe and expect it to work.)
Bottom line, if he cannot control what does/does not go into his mouth, knowing what his doctor said, then he needs to stay home. It's not anyone else's problem.