That sounds, if anything, like an injunction against killing your enemies - he's saying that these cities will suffer on the day of judgement, rather than encouraging people to make them suffer in the present. Sounds a lot more like an argument for leaving the punishment of wrongdoers up to God.
I agree with your assessment of the quoted verses. It also seems to me that given the message of those verses, one would have to be against any form of man-made criminal justice system if they want to claim to be a true Christian.