All those Bible quotes refer specifically to apostates (ie. people who used to belong to the Jewish faith, but then left to follow other gods). I'm not saying that this teaching isn't despicable, because it is. But Islam teaches the same thing, AND they add the commandment to kill ANY and ALL non-Muslims on top of that. Sure Christianity teaches some evil, but Islam teaches that same evil plus an extra, heaping topping of super-evil!
Now, how do you know that?
If you're a Christian, you've been trained in hermeneutics so that you can interpret your book. I, as a non-believer, cannot interpret it the "right" way. I don't have that training! So to me, it says "kill all non-Christians." I just don't have the historical context.
I believe you're capable of extrapolation.
I am not a Christian, although I was raised as one. But I am able to read, whether or not I am trained in hermeneutics. For example, when a verse says that a person has "transgressed his covenant," what else could that mean, but that they had a covenant in the first place? You cannot transgress a covenant that you never made.
2 Chronicles 15:12-13 may sound similar to the quotes I gave from the Quran, but, if you actually read the whole verses, rather than the little snippet that Glyph provided, you'll see that it is actually part of a promise that certain Isrealites willingly agreed to. "And they entered into a covenant to seek the Lord, the God of their fathers, with all their heart and with all their soul, but that whoever would not seek the Lord, the God of Israel, should be put to death, whether young or old, man or woman." Basically they are saying, "We promise to always follow God. If we ever cease to uphold this promise, kill us."
That is VERY different from Allah commanding his followers, "Kill anyone who doesn't believe in me."
To me, they're both just books, and both of them advocate a lot of weird stuff if you look at them without any historical context.
To me, historical context doesn't matter as much as you suggest, because the people who follow these books claim that they still apply to our day. A book that teaches that you should stone apostates teaches that you should stone apostates. The fact that the book is old, and maybe that was more morally acceptable back then does matter one sausage if people today look to that book as though it were still a valid source of moral guidance.