I believe that the Sikhs place a very great religious significance on the kirpan and that to use it wrongly is a great sin. It is, as far as I know, drawn only very, very rarely on other than religious occasions.

With rights go responsibility. If you grant the right to carry a dagger because it is part of your religious beliefs, then you have a corresponding responsibility regarding its use -- just as you would have carrying any deadly weapon.

Having said that, remember that I contend that anything can be used as a weapon. The fact that you have the ability to kill another places upon your the responsibility not to do so except in the gravest circumstances.

But I will posit a gnu question: Suppose a culture requires cannibalism of its dead (as still is the case in some places)? Suppose religion requires ritual cannibalism of its founder? Should either be banned?