It is not uniquely Christian to practice self-defense; it is simply human, and part of the moral law (the flip side of "do not murder" is having the right to not be murdered), and part of the code governing the common kingdom (aka the Noachic covenant in Gen 9).

I wouldn't say Christ calls us to use violence or aggression to drive out sinners. No. Not at all. Defensively? Yes. He has already done the cleansing and the disarming and will return to finish the job. Doesn't mean we can't seek justice and honesty in contracts and commerce now, though. Just not violently.