Even if Wink's (?) interpretation of "other cheek" was historically correct (I have no clue), it is wildly out of context of the passages where the phrase is used. The message is to not retaliate. Also, in practical terms, you can effectively defend yourself without punching back i.e. causing harm. Eventually, the aggressor will tire out. Of course it's not for the faint of heart and most people will think you are a "small cat" (but you also won't be attacked again by the same aggressor you successfully defended yourself against, at least AFAICT).