I think what we need to accept is that a replica gun can be used by any idiot to hold up a pertrol station etc. Also, being replica of a ranged weapon, there is no way to run. With a sword or other melee weapon, first it takes a lot more skill to wield and secondly you can run away without risking being shot in the back.

There is also the practical side of things. Blades have uses. If you ban a sword or dagger you need to ban kitchen knives, etc. Pistols have no non-violent use.