Bones, Season 6

Booth:
We're gonna get this guy and he's not gonna keep doing this.

Brennan:
Your words are quite ironic.

Booth:
What do you mean?

Brennan:
I imagine Broadsky would say the same thing as he stalks his prey.

Booth:
Except I'm the good guy, he isn't.

Brennan:
But you both led a life in which you were paid to take lives.

Booth:
Why are you doing this?

Brennan:
I just like to understand. I admire your certainty but since good and bad are such subjective concepts, how could you ever be sure you're doing the right thing?

Booth:
Ok, well, it's not subjective to me. I mean there's good and there's evil. Life is all about taking sides. Broadsky? Well, he joined the wrong team.