The psychopaths who declare themselves sheepdogs and disparagingly call people who can feel emotions "sheep" suggest that psychopaths think that people who can feel real emotions cannot defend themselves against psychopaths. Why do psychopath people think that people who can feel real emotions cannot defend themselves against psychopaths?
Well, it's a deleted account from a year ago, so acknowledging that I'm talking to dead air here...
But, the speech being referenced here includes three categories of people: "sheep," sheepdogs," and "wolves." In the context of the speech, the wolves are metaphors for the psychopaths: the bullies and cruel sadists who tread on others. In the speech, "sheepdogs" protect others from the wolves.
Now, the scene is more complex because the dad is taking out his belt to "whup" his kid, and we the audience get to decide whether or not we agree with that or not. We get to contemplate the kind of mentality that divides people into those camps or thinks that somebody who isn't fighting is or is not a sheep. I think this movie actually gets called one-dimensional or accused of being just a pile of testosterone and apologetics for the Iraq War and that's not fair because it just isn't doing our thinking for us.
For my own two cents:
I'd say that we do live in a world where there are cruel people, kind people, and people who can/do defend others - especially weaker people. The speech kinda bears out, and that might suck, but it's largely the truth. I'm not sure I'd classify the people who can't (or don't) physically defend themselves as "sheep". That's a bit much for me.
But if the core of the message here is that we should take responsibility for our actions and for standing up against bullies, yes, I'd agree with that.