I wouldn't quote the scripture to unbelievers. That's just not something that's likely to impress those of us who don't believe. So, at least don't leave it on its own. Explain what it means to you, and remember that your own explanation is the part they will be paying attention to. The scripture itself will most likely be in one eye and out the other, particularly if you appear to be relying on that instead of presenting your own opinion.
I have my own concerns about the role of religion in terrorism, etc., and so I would most likely be on the other side of this, but if you are characterizing their views accurately, then their position can be taken down a notch or two. I can't think of any acts of terrorism done in the name of atheism itself, but I'm quite certain that there have been atheists who committed acts of terrorism. So, the trick is to look at the positive causes that atheists might be interested in. Take for instance socialism and/or anarchism. I may be wrong, but I believe the anarchist movement that Sacco and Vanzetti were involved in had more than a few atheists (I can't remember, but I think one or both of them were atheists). If the other side says that they were framed, say yes, for that crime in particular, but the organization in question did bomb a number of people ('propoganda by the deed', they called it). Of course you could always point to Marxist excesses. Anyway, remember the trick will be to get past the negative position (atheism) which isn't much worth killing anybody over, and look at the various positive beliefs that different atheists DO have (that's what people are willing to kill over).
Finally, may I suggest that you take seriously the contention that religion does play a role in promoting violence. What that role is, and whether or not it is a good reason to abandon your beliefs are very different questions.
