Exactly what the title says, Christianity in all its various strains still stems from the horrendous old testament, and with all the awful shit that endorses, as well as with things like Calvinism and the general doomsday cult foundations in the religion, why do some people still act so charitably towards it? Christianity has proven itself to be a morally corrupt and oppressive institution at every turn. Or maybe I'm just too negative? 
EDIT Ok guys I get it this was rather reductionist, and I definitely was disregarding all the good that religious folks have done, and that religion has inspired people to do, but again over correcting into enthusiastic support for religion can also be problematic.
i've had more luck in my personal life pushing left curious Christians further left using this methodology. i don't belitte their beliefs just reinforce the good stuff, focus on the institutions, etc. there are legions of seemingly "socially conservative Christians" out there that are actually just nascent christian socialists but just don't know that's an option because all they see on TV is demonic Prosperity Theory grifters and psychotic fire and brimstone shit