Jacob is not speaking selfishly. He is the patriarch, the holy seed, the head of the family of promise; he speaks as representative of that family.
How do we respond to correction and rebuke? It is one thing to run into the lash of a tongue. The normal reaction to that is to cover up and protect ourselves, and feel very little by way of conscience. But when we see real grief in one we respect on account of what we have done, that may bring us to our senses. There is here a pattern of correct reproof. He doesn’t berate, harangue, or pour abuse, but he remonstrates in terms of what Simeon and Levi have done to the family. Sometimes it is necessary in the church when the church is brought into disrepute – someone has behaved in a shoddy way, and cared nothing about the good name of God’s people. The same is true of the family. We have to be careful about this: in a large city we become somewhat anonymous and we think we can get away with evil deeds without anyone noticing.