In many ways, I’m in close agreement with Another_Damned_Medievalist — there are serious dangers in the presentminded approach that some people bring to the study of history. When you go to history with the express purpose of justifying your own or others actions and viewpoints in the present, that should raise a red flag. You’re not doing history, you’re using history and while that use may be educational and helpful in the present, it often ends up hopelessly skewing any understanding of the original society.
This is doubly parlous when it’s the teacher or professor offering up the modern parallel, explanation or context that some will take away as the only explanation: if we teach Magna Carta as the precursor to the Bill of Rights, students pigeonhole the two very different historical documents and contexts together (grossly incorrectly, too, in my view). I am always chary of using any of these parallels and, perhaps driven from my own interest in the history of texts and intellectual culture, spend a fair bit of time in class exploding students’ confidence in their ability to superficially read historical documents.
Original? Didn’t mean now what it means then. Family? Ditto. Terms that we throw around comfortably in our own context can take on subtle or radically different implications in the past. And to let someone cherry-pick or blithely pigeonhole the past without understanding that is to betray the very basis of our discipline.