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.
a) institution is not religion tho, beliefs are what you make of them
b) new testament is compatible with socialism in myriads of way (one might say suspiciously so :lunacharsky-shining:).
c) soviet crusade against religion was wildly unsuccessful, to put it mildly (both at home and especially abroad). you come at 2000 year old institution, you best not miss and things of that nature
d) ...last sigh of the oppressed implies until there is memory of oppression you can't jettison religion, not really, until people can control their fate, they'll always be religious in some shape or form somewhere
There's also a myriad of ways it is not. You won't find a less dialectical materialist analysis than the sermont on the mount
i'm just saying, with the situation the left and the world is in, and adding historical experience, i think it's counterproductive to dismiss religion flat-out (or rather engage in pointless fighting around it, we don't have power to change it, and religions have some affinities we can draw on, depending on religion/means of production development/society safety nets as they are/depraved profit seeking stage)
It is valid to highlight the good done by Christians and the ways in which Christians can support and be a part of a socialist project, but I don't think it's necessary to pretend that the new testament is inherent socialist to do so.
i'm saying socialism bears the mark of christianity (either by emphasis or by negation), not the other way around tbh. plus dialectical materialism doesn't inherently contain ethics or morals, people just input their own.
i'm absolutely whatever on people hating christianity due to their own horrible experience, that's fair enough, just as it's fair for people in shit situations to embrace it. dismissing it however, as non-productive/non-compatible with our goals, is judging by history, not a great idea. *it's non-compatible with feuerbach religion development which marxists typically use (i think its feuerbach?) and thus with ontological view in general, but compatible with goals with some shenanigans on emphasis, same as anarchism tbh.
If you claim that every major group that claims to be christian is not actually christian, then what claim do you have to be an actual christian instead of them?
Also, if you consider every such group to not good, then why do you want to base your beliefs on their fiction that they consistently use for horrible stuff that ranges from abuse on a personal level to colonialism, slavery, and genocide?
cause i'm more christian than they are, literally same claim they make. if your christianity consists of 15 minutes in sunday church and denial of benefits in your work time or making bombs, i do think you are not a christian, i don't give a flying fuck what your priest says about intentions. If your faith consists of hating people, as it's the lowest form of prayer to hope for misfortune of your enemies, i do think you are full of shit. (and i'm agnostic, cause i think christians are full of shit as a whole, but i do recognize that my morality was significantly influenced by christianity either by osmosis or bible)
if you think colonialism, slavery or genocide wouldn't happen without christianity, i do suggest hitting some books one more time (or many more times). (i do think homophobia is very traceable though).
So, you do not have any more basis for your claims than they do? Considering that, and the fact that they outnumber you by a lot, it seems that they are better candidates for being classified as actual christians.
In that case, christians can be divided into being full of shit and ones who base their beliefs on the claims of the ones who are full of shit but with a few deviations.
I don't, but christians and their organisations have been consistent supporters of such. The rest still has their beliefs entirely on the say-so of those (with, again, some deviations).