As christians are we called to simply endure certain injustices? If so when should we not endure them and respond the justified anger? Moreover, I am confused about whether justified anger is simply refering to a feeling or the way we act.
Bearing wrongs with patience is a spiritual work of mercy. Just be certain that you are the one being wronged. This does not give anyeone else license to abuse you. I do not know the entirety of your circumstances, but a human trait is to be more upset about the conditions of others than they are - this is not spiritually healthy. Bearing in mind that one should/must help if that person is powerless to improve their lot in life.
Anger is a passion and is not in itself sinful. It is intended to motivate one to oppose evil - our Lord was angry at those who defiled the Temple, for instance.