Because Christianity has been used as an excuse to carry out hateful actions throughout history, and, from what I can tell, it's far from what it originally used to be. In a sense, it's corrupted. Of course that doesn't mean all factions of Christianity are corrupted, nor are the believers of it, but some still use it as an excuse to hate.
And cause western influence is everywhere. Even if they made up a religion, it would likely derive strongly from Catholicism.
Also, Catholicism is often considered the most tolerant or forgiving of all religions. If you attempted a similar story with another faith, it might spark significant backlash.
Good point
It's confusing how it's so accepting, yet so- not, at the same time.
Why bro, just make up a fake religion whyd it have to be Catholic TvT