Sure, atheists fight amongst themselves as much as any other group. Not everybody likes the RRS, for instance. The difference from religions is, we can't resort to schisms in order to draw clear battle lines. When it happens, we respond like people do in any non-religious argument. We reply, we rebut, or we rebuke. Sometimes, unfortunately, we retaliate. We're human.
Everybody knows that people will sometimes attack and betray each other...including the authors of the Bible. Passages like those you mention use the observational fact of constant human conflict. All the authors do is predict based on their own observation that it will continue, in other words human behaviour will not change in the forseeable future, any more than it had in the thousands of years of history available to the authors. I argue that the Bible is wrong in many of its claims, but nobody's saying there isn't a single true word in it.
Approaching this prediction using my new reference post on prophecies and predictions, it fits squarely into the first suggestion: High Probability of Success. It is indeed an implicit prediction, and it is correct so far, but it was pretty darn easy to guess. Did it really need to be divinely inspired to be accurate?