I don't think the clip is making fun of people who eat gluten-free, it's making fun of people who follow dietary advice without any thoughts and reasons why they should other than to be cool or lose weight.
For some, being gluten-free is a prescribed treatment for their disease. For other's it's just a diet.
But I know what y'all mean. It makes me quite angry when people start referring to "the mediterranean diet" as if it's some sort of diet to try for weight loss. Uhm, no - it's the way people eat in the mediterranean.
"No matter how developed you are in any other area of your life, no matter what you say you believe, no matter how sophisticated or enlightened you think you are, how you eat tells all." - Geneen Roth