what remains of usury, if you should be believers. And if you do not, then be informed of a war [against you] from Allah and His Messenger. But if you repent, you may have your principal—[thus] you do no wrong, nor are you wronged} [Al-Baqarah: 278–279]. {Your principal}—meaning without any addition—{you do no wrong, nor are you wronged}.
Yes, if it is assumed that the revenues of these banks return to this oppressive government, then this might be a justification to take this usurious interest in order to ward off injustice from yourself, because you would be taking it from the oppressive state to ward off its oppression. However, if these banks do not belong to this oppressive state, then I do not view it as permissible to take it, even though some people issue rulings that one may take it not with the intention of possessing it, but rather to prevent it from being channeled to Christian institutions. For some claim that if you do not take this interest, these banks will spend it on calling to Christianity, which they call missionary work (tabshīr), though we do not know whether this is true or not.
In any case, the summary of my answer regarding this issue is that it is not permissible to take usurious interest (ribā) from banks due to the saying of Allah the Exalted: {O you who have believed, fear Allah and give up what remains of usury, if you should be believers. And if you do not, then be informed of a war [against you] from Allah and His Messenger. But if you repent, you may have your principal—[thus] you do no wrong, nor are you wronged} [Al-Baqarah: 278–279], for He explicitly restricted it to the principal amounts.
Furthermore, the Prophet ﷺ said in the sermon of ʿArafah during the Farewell Pilgrimage—the largest gathering of the Islamic nation: "Indeed, the usury of the pre-Islamic era (jāhiliyyah) is abolished, and the first usury I abolish from our usury is that of al-ʿAbbās ibn ʿAbd al-Muṭṭalib; it is entirely abolished." So consider: a usurious contract was concluded during a state of polytheism (shirk), yet the Messenger ﷺ abolished it