This part of 'what your bible says about murder and poor people' makes it sound like the writer of the response believes it's causational but i think they were just offended and not trying to make a scientifically sound argument. And i would understand that.
It's almost racist because of how the first post makes Christianity sound like something superior. As if the Japanese being different in their believe makes them less.
also wouldn't it make complete sense for Japan to have way less Christians since they were isolated for so long and have their own religious beliefs
Exactly this. Although Japanese rulers haven't always been very peaceful, their culture is known for being caring and respectful towards others where as Americans are by many people seen as loud and obnoxious (also positive things, but i'm not trying to make a comparison between two cultures as a whole), making this comment about Japanese adoption of Christianity not only come across as ignorant but also very arrogant.