Jesus told Peter to put his sword away not because using a sword was always wrong, but because (as Jesus told Peter) he had to fulfill his mission on the cross, and the apostles' opposing that would be wrong.  Note: Jesus did not say, "What?  Where you get THAT?  Didn't I tell you to never use one of those things?  Great.  Now they's all think we're right-wing NSA (National Sword Association) nuts."