Is the preceding quote from the Sermon on the Mount a universal moral precept? It would seem not. Commenting on John XVIII, 22-3--"And when he had said these things, one of the servants standing by, gave Jesus a blow, saying: Answerest thou the high priest so? Jesus answered him: If I have spoken evil, give testimony of the evil; but if well, why strikest thou me?"--St. Thomas Aquinas says the following:
So Sacred Scripture is to be understood according to all that Christ and the saints have kept. Christ did not offer His other cheek, nor Paul either (Acts XVI, 22ff). Thus it is not to be understood that Christ has commanded everyone to literally offer the physical other cheek to he that strikes someone; but this ought to be understood as preparation of the soul, that if it will be necessary, one ought therefore to be disposed to not be disturbed in soul facing a beating, but let one be prepared for the like and to put up with more besides. And this the Lord kept, whereby He offered his body at the fit time. So therefore this action of the Lord is useful for our instruction.1The passage in Acts that St. Thomas references is when Paul and Silas were unjustly beaten and imprisoned in Philippi. When they were to be released the next day, Paul refused until the magistrates came and released them personally, for Paul and Silas were Roman citizens who had been beaten and imprisoned unlawfully. The Douay-Rheims commentary on Matthew V, 39 also references Acts XXIII, where Paul, upon hearing that some Jews were planing to kill him, sends the witness who brought him this information to the tribune, who in turn called for soldiers to protect Paul from the attack.
Thus, the meaning of the passage in Matthew cannot be that we can never resist evil, and instead always suffer in silence. Christ Himself rebukes injustice rather than offer His other cheek for striking. Paul utilized his full legal rights, as a citizen of Rome, to protect himself from evil and to rebuke those who unjustly did evil to him. Rather, the verses encourage the Christian to bear evils he cannot avoid or defend against with patience and love, praying for the good of those who harm them rather than hating them and wishing evil upon them. But if a Christian can morally defend himself and others against evil, he may do so. Nothing about defending against evil requires hatred or bitterness instead of love. Love and resistance to evil are not mutually exclusive.
1 Super Evangelium S. Ioannis, cap. 18, l. 4: "Sic sacra Scriptura intelligenda est secundum quod Christus et alii sancti servaverunt. Christus autem non praebuit isti aliam maxillam: nec Paulus, Act. XVI, 22 ss. Unde non est intelligendum quod Christus mandasset quod praeberent maxillam aliam corporalem ad litteram ei qui percutit unam; sed hoc debet intelligi quantum ad praeparationem animi, quod si necesse fuerit, ita debet esse dispositus ut non turbetur animo contra percutientem, sed paratus sit simile et etiam amplius sustinere. Et hoc dominus servavit, qui corpus suum praebuit occisioni. Sic ergo excusatio domini utilis fuit ad nostram instructionem."