Christians celebrate rape, torture, slavery and genocide.

[Kirbmarc]

let alone quantify everything since the inception of Christianity.

Maybe not, but we can look at the historical evidence and take into account the extremely harmful potential of religions and dogmatic ideologies in general.

What if we employ seemingly empathic deeds for selfish motives? This seems very common to me, and I believe is backed up by research (observing what people do if they think no one's watching vs. if someone's standing there).

Empathy is not the exact opposite of selfishness, it's opposite of sociopathy. We need to acknowledge that someone is there to be empathic to them.

Even if we are highly empathic, we can easily fool ourselves into believing that no one is going to harmed by a really harmful action if we don't have direct evidence of a harm being done. Confirming your own bias is very simple.

For example, polluting is potentially very harmful. But since there's rarely an immediate, visible harm caused by pollution, it's not hard to pretend that nothing harmful is going on. People who pollute a lot, however, can't be reasonably called evil, or sociopaths. They're simply deluded (or uneducated).

Sociopaths harm people directly and acknowledge what they're doing. They simply think it's within their rights to do so.

And again, it's impossible to quantify.

True. However, we can quantify the social impact of religious morality as a whole. And the results don't look very good for religious morality.

It's not necessarily an un-Biblical position.

I'm surprised by this statement. The Bible promotes religious morality, why should a believer think that religious morality does more harm than good?