Acceptance of injustice in any form (sexism, for example) makes people think unjust behaviour is acceptable, meaning it will be easier for other forms to happen (racism, for example). Thus, it can manifest into many different spheres.
Also, the action of one person doing something unjust can persuade others to similarly act unjust, as they do not want to miss out on the potential quick benefits offered to them through his misbehaviour.
The importance of diversity is paramount in the multicultural world we live in, and injustice in any facet of society will prove detrimental to our development and well-being as a whole. Injustice to one culture means potential injustice to all cultures including section of the majority culture.
If any of us can be singled out and turned servile, then all of us are at risk. The only chance we have is if the law protects every one of us equally, protecting some a little more is acceptable if they are vulnerable.
If there is an injustice, something that is unfair, to someone, even if they are not close to you, it allows the possibility of another injustice and then another until the justice that you enjoy, that you take to be a right of yours, may not be there for you as it has been denied these other people. so it is very important that you support justice for everyone, everywhere, to prevent the loss of justice for yourself.
Just because someone is of a different religion, or comes from a different section of town, or has a different family background, or has a different history, or has a different education, or a different sexual preference, or has a different ethnic background, or is of a different sex, or has different physical defects, or different height challenges, or different mental capabilities, or are of different ages, you would be unwise to tolerate injustice toward them for any of those reasons, because you then may find yourself in a group that injustice is practiced against. So even if you may not see eye to eye with someone, you still need to believe in the need for them to have their liberties protected.
Too often people believe in rights and justice only for themselves. For instance, ‘freedom of speech’ to many people means only freedom for themselves and whoever agrees with them. Even today there are people who believe freedom of religion only means freedom for -their- religion.
Before the Civil Rights era in the USA, many people fought for justice only for the middle class, for white people. They didn’t care how blacks were treated in the South, or how disadvantaged people were treated just about everywhere. King was reminding us that justice is not justice until it applies to everyone.
And though we’ve made considerable progress in 68 years in India years, we still have one kind of justice for people who are well off and another kind for everyone else. One kind for one sex and another for the other. One for one caste and another for others.
“We are caught in an inescapable network of mutuality, tied in a single garment of destiny. Whatever affects one directly, affects all indirectly.” Martin Luther King Jr