"I'm NOT going to eat it (the one bite of spinach) and you can't make me! You're the meanest mom in the whole world! My taste buds just don't like it. It's all Olivia's fault because she ate hers and now I have to eat mine, but I'm not going to! I don't care if it will make me strong! When will my taste buds grow up? You're so mean!"
And on, and on.
(I realize you can't see the spinach on his plate and may think he has already tried it. Nope - he tried to hide it in a bite of chicken pie, but then still couldn't bring himself to put the bite into his mouth.)