[ralferoo]

The issue isn't really whether a Sikh might be carrying a knife (as Sikhs generally advocate non-violence and pacifism), but if an exemption is afforded to give Sikhs the right to carry weapons on a plane, whether a terrorist might then impersonate being a Sikh in order to get a weapon onboard.

[mothballed]

The Sikh blade is ornamental, and usually blunted. There's no reason why they shouldn't be able to carry a blunted blade that basically isn't even a knife. There is no concern of a terrorist using it anymore than any other blunted object, as Sikhs could be required to bring the blunted blade and the blade checked at security.