This is a cosmetic removal mod. There are many like it, but this one is actually on the workshop.

By checking this box your game will hide every known pathogen of in-game personalization: headwear, footwear, facewear, even unusual particle effects. But only for you, of course.

What more needs to be said? Wipe the slate clean. Make the game like it was meant to be... undisturbed by hats.