This is an interesting story. It's not often talked about in Christian churches, and I'd never been taught the story before. It's a really difficult and confusing passage. We mostly talked about it in the context of honor killings, and of the marginalization of women in the biblical text. The Rabbi mentioned a comparison to The Godfather again, this time in reference to Jacob.
I understand it as an unethical overreaction to an incredibly difficult situation. Key parts of the story are missing. We don't know how Dinah felt about Shechem. Even that brings up the question of whether or not that matters. If it were a date-rape situation, would that make it less wrong? And if Shechem's actions weren't morally reprehensible, what effect does that have on the reaction of Dinah's brothers Simeon and Levi? It would seem that their reaction would be even more extreme and difficult to understand, and very unethical.
At the same time, Simeon and Levi come off very badly in the story, and it seems that the author is trying to paint them as unethical. It's all very much a gray area, though. Jacob rebukes them at the end of the story, saying that their actions have made him and his people look bad. It's a very weak admonition, and it's not even the last word in the argument; Simeon and Levi get that, in defense of their actions.
It's an extremely challenging text, and I really don't know what to think of it, other than to realize that there are as many reactions to a situation as there are people. Beyond that, there are a million ways to interpret the behavior, especially when it's recorded forever in a pretty cryptic fashion.