There is all the difference in the world between the nonviolence that the ordinary Christian should embrace and the duty of civic authorities to police their communities. The end of Romans 12 is quite clear about the first; the start of Romans 13 is quite clear about the second.
N. T. WrightI came to Paul at quite an early age, having already studied Plato and Aristotle; and I found Paul easily their intellectual equal, though he was handling these amazing questions about God, Jesus, Israel, faith and so on. He continues to be an amazingly stimulating thinker, especially when we try to understand the flow of thought in letter after letter rather than just combing him for a few verses on 'our favourite topics', which, sadly, some Christian teachers do just as some journalists and broadcasters do!
N. T. Wright