Who made up the "rule:" for "opposing injustice it is allowed or good to feel angry"?

Many people write online, that they are angry about injustice, despite EVERYONE KNOWS anger is bad in family situations, but still many write and read online that anger is allowed or good to respond to or oppose injustice... but who made it up?

Some people just wrote it and it caught on? And if so how can anyone be a GOOD PERSON, without the new testament, that said anger leads to killing, so EVERYONE must stifle anger?

Who made up the "rule:" for "opposing injustice it is allowed or good to feel angry"?
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