“Free speech culture” means that you can call for censorship, disproportionately abuse other people for speech, chill and deter people for speech, even call for violence against others so long as you do it in certain ritualized and stylized ways that people who were on the debate team like. If you dehumanize fellow Americans from a lectern or with a debate moderator or as a contributing writer to a magazine, that promotes free speech culture; if you do it in a social media post denouncing the speaker, or from a protest outside, or in a letter to the Dean, that harms free speech culture. “Prove me wrong” is a magical incantation that renders what follows pro-free-speech-culture.
Excellent description of how the term "free speech" means something very specific in maga culture.