Perhaps you can rephrase this quotation thus: "If you are prepared to use force to defend civilization, then be prepared to justify barbarism." - not that i don't sympathize with the sentiment of the original quotation, but too often the need to resort to force is a symptom of 'uncivilization' ie a society that is not civilized.
If you are not prepared to use force to defend civilization, then be prepared to accept barbarism. 
To deal with men by force is as impractical as to deal with nature by persuasion.