Finished watching the Third Season (again) with a friend who missed the last half of the season because he dropped his cable. Anyway, we were talking about what Carl does near the end of the episode and we were both pretty much in agreement that what Carl did wasn't "that bad."
Carl told the kid to drop the rifle and the kid was more handing it over which could put Carl (and further Hershel, the baby and Hershel's younger daughter) at risk as Carl would have to lower his own weapon to retrieve the rifle. In this kind of world and climate why chance it and "trust" anyone? You tell someone to drop their gun and they don't and, instead, sort of slowly hand it over why take the risk that something will go wrong by lowering your own guard to get it. Hell as a policeman Rick should get that. (Though he wasn't told the whole story/details by either Carl or Hershel.)