I think we've covered the idea of "should versus Could" on the show... do a search here and you find a few threads touching on the topic.
It is hard to do comprehensive TV that applies to all jurisdictions when it comes to the nuances of law and case law... the good news is, as you'll see in those other threads, I think that the law is irrelevant to the question of WHEN to use force to defend yourself. That should be based on perceived NEED, not the legal option.
-RJP