I suppose it comes down to how you were taught the meaning of the religious doctrine you follow/inherited/deny.
I was raised C of E and can categorically say I have never been told sexual slavery is an acceptable practice. Nor was I molested by a priest.
I have never seen a member of the religion I follow/inherited/deny lop some blokes head off and say it is justifiable either.
But that's just the 'bad ones'.
So was I raised C of E, and neither have I been told that sexual slavery is acceptable, and I absolutely don't think that right thinking Christians will believe it is acceptable; any more than I believe that right thinking muslims will think it acceptable either. The "debate" was simply in response to the incorrect point that the Koran is the only holy text that has a passage that can be interpreted in that way.
To your murder point: Maybe not, but we have seen a British soldier shoot an unarmed combatant lying at his feet and telling the squaddie standing next to him to not say anything as "that didn't happen".