All of the Abraham religions have proven themselves to be a boil on the ass of humanity. Alongside some of the worst atrocities in human history (slavery, colonialism, anti-semitism), you can find them there condoning the acts. If there's a demon or a devil, billions unwittingly serve him.
After I left organized religion, I still considered that everyone had the right to believe what they want. The problem is that, at their core, Abrahamic religions are thinly veiled political statements that dwell on issues of dominion and rulership OF THE WHOLE EARTH (heck Universe). Thefore adherents often have an annoying and dangerous tendency to seek to make THEIR beliefs YOUR business.
While this is not the central appeal to all adherents, it does represent the core of those religions and ignoring those aspects essentially neuter them. That's why the "radical" and "fundamentalist" elements can rightly chastise the "moderates". The moderates have to ignore a whole lot of their religion so as to not look batshit insane in a modern secular society.
Zyklon B was deadly, but it was Nazism that put it to use as a tool for genocide. I'm no big fan of guns but the ideology was the core issue here.