Further proof, if any were needed, that our nation is young is this sobering fact: I have been alive for slightly more than 25 percent of the time since 13 colonies declared their independence. (As Benjamin Franklin once told me … well, never mind.)In that time, I have seen a U.S. president shot dead (Kennedy), another president shot but not killed (Reagan), a president shot at and missed (Ford) and a presidential candidate shot dead (Bobby Kennedy).I have seen a president resign from office (Nixon), a president …