The rationale of a kid in London who carries a knife for self protection is the same as that of a grown American who gets a gun for self protection is indeed the same. The difference is that the former is recognised generally as acting in a stupid, antisocial and self-destructive. There is no equivalent of the NRA supporting and encouraging him, or defending his right to have thatknife. And there is no mass of knife enthusiasts with deep pockets who have purchased the loyalty of corrupted politicians.