Simeon and Levi answered their father Jacob with a question that has rung through every generation since. Targum Pseudo-Jonathan (Genesis 34:31) gives them a longer speech than the plain text, and it is worth hearing in full.
"It would not have been fit to be said in the congregations of Israel that the uncircumcised polluted the virgin, and the worshippers of idols debased the daughter of Jakob. But it is fit that it should be said, The uncircumcised were slain on account of the virgin, and the worshippers of idols on account of the daughter of Jakob. Shekem bar Hamor will not now deride us with his words; for as a whorish woman and an outcast who has no avenger would he have made our sister, if we had not done this thing."
The question that has no easy answer
Every society has to answer their question: when someone harms your sister, who will answer for it? The brothers' logic is stark. If no one answers, then Dinah has been treated as a woman with no protector — the category the Torah calls zonah, an outcast. Her honor depends on her brothers' willingness to act.
Jewish tradition has never fully endorsed what they did. But it has also never fully condemned their question. Their question is right even when their answer is wrong. Dinah was not nothing. She had brothers. And the brothers insisted she be remembered that way.
The takeaway: sometimes a terrible act springs from a true question, and the terrible act is still wrong — but the question remains true.