I'd need an elaboration of what you mean by "anti-Catholic", just out of curiosity, but I'm pretty sure I'm not a fan of "Christian hardcore" regardless.
See those lyrics above. Basically lots of Christian hardcore bands and Christians in my whole subculture in general aren't fond of Catholicism because in addition to being very socially reactionary it is also very hierarchical and ritual-driven instead of focusing on the relationship between a person and God alone. It should obvious why someone who likes to go moshing at house shows and spend $30 apiece on limited edition colored vinyl records isn't going to want to base their life on the edicts of some 80something German guy and a bunch of similarly old celibate men. It also represents authority and force and obviously is quite "mainstream". Most hate megachurches and the prosperity gospel in the same vein, too big, too money-focused, too mainstream and too incompatible with counter-culture, the MTV of Christianity in a sense.