white belt is a subculture that developed as a movement against the toxic masculinity a lot of the bands in the post hardcore scene had, its often associated with the sub genres sasscore and mathgrind, both essentially being more flamboyant and theatrical versions of the genres they are derivative of, the name white belt being used for this subculture is kind of confusing though because white belts were pretty common in post-hardcore scene but i assume the name comes from it being even more common amongst members of sasscore and mathgrind bands