Another reason sometimes a person--who may have caught a glimpse of life in the Spirit--quickly runs to legalism to secure their Walk (and thus, sadly also quickly blocks the Spirit's work) is because of hidden rebellion and cowardice.
Some people are just by personality and nature . . . timid and horrified by conflict of any kind. These are they who may be those, for instance, who can't hardly stand even the sight of a gun--are loathe to touch one, let alone have one in the house. If someone were in trouble, or even themselves, they run to "turn the other cheek" as a justification and excuse for NEVER responding forcefully to an attack. I am referring to someone who is simply a coward and uses a legalistic norm to cover their lack of defense. They are not turning the other cheek so much because they love Jesus and obey the Holy Spirit, but because they love themselves and their own comfort that they want to avoid any and all situations where a forceful response is warranted and even required.
Also, the other lure of legalism kicks in where this person can now feel "better" than others who do not absolutely follow the rule, ie., "never violence, never defend" . . . . They will delude their self into thinking it is because they are so "loving" and "peaceful" and "Christlike" that they assert the law of pacifism, but, ironically, the instant legalism enters, love leaves in actuality.
It happens in churches all the time. There is a "rule", for instance, that people should "dress nice" . . . "sit up straight" . . . "attend every Sunday" . . . and those who love rules are eager to comply . . . but right away, they are also the ones who sit in the pews looking around the room to see who is NOT complying. Love is gone and in its place is "holier than thou" . . . judging, condemning those who . . . don't "dress properly" . . . who slouch . . . who sometimes skip church etc.
There is also a rebellious spirit, again ironic, attendant the legalist. How so? Often, they don't really want to submit to God's will, which requires an ongoing, living relationship and just want a rule or law they can follow, so that they can claim obedience, saying, "look at me, I follow such and such law, ie., 'nonviolence'" but then those areas of their life not covered by law, they do whatever they will, believing that they already "gave at the office." What if Holy Spirit prompts someone in a certain situation to grab a gun and defend another? The secretly rebellious and cowardly can say, "sorry, I follow the rule of nonviolence, so I cannot obey the Spirit."
When an enemy is persecuting you individually . . . turning the other cheek and deferring time and again returning not evil for evil, shows the loving, longsuffering, self sacrificing heart of the believer. Where others are involved--and where the individual may be responsible to and for a group, defense of the weak and helpless also shows the same love , self sacrifice and longsuffering . . . . I humbly submit . . . .
What do we about Rahab who lied to save two spies and was later blessed by the Lord? Would I steal to feed my starving family? Honestly, I don't know. I might. I might not. I am a sinner, that I know. In such a situation I would like to think not, in being obedient to the commandments. However I do not recall a commandment "thou shalt not defend thyself or loved no matter what." There is one about murder, which is the taking of innocent life.
It appears God does allow self defense, however.
"If the thief is caught while breaking in, and is struck so that he dies, there will be no bloodguiltiness on his account." Exodus 22:2