The efforts of institutions to eradicate hate both within and beyond the sporting domain have led professional football leagues such as the Premier League and La Liga to develop their own anti-racism campaigns. This study examines X users’ reactions to posts published by each competition under the slogans No Room for Racism and LaLiga VS Racismo. Through a longitudinal, mixed-method analysis, (
= 238) posts and (
= 20,329) responses were examined to assess the evolution of online discourse, the level of hostility, and the degree of polarization surrounding these campaigns. Our findings indicate that hostile discourse tends to emerge sporadically, particularly in response to visible social events rather than as a direct consequence of the campaigns themselves. Qualitative analysis further shows that a substantial proportion of toxic or negative responses does not stem from overtly racist discourse, but from users criticizing the perceived effectiveness or constituency of the campaigns. The results also reveal differences between the two leagues: while the Premier League exhibits a relatively balanced distribution of positive and negative responses, La Liga is characterized by a predominance of negative affect. These findings contribute to the literature on sport, racism and digital polarization by showing how institutional anti-racism campaigns become embedded in broader conflicts over their legitimacy and effectiveness.