I am a firearms enthusiast, myself, but I think I'd concede that the decline of the sword, and the attendant advent of firearms did have a decivilizing effect on society.
Actually the advent of the firearm, along with the ability of the yeomen to stand against the armored noble, probably helped usher in the era of the rights of everyman, rather than just the rights of nobles. While militia like entities did exist before firearms, it was only the advent of the relatively inexpensive and easy to use firearm, that made mininmally trained militia armies effective on the battlefield. One they had the guns, how could the fuedal Lords continue to subjegate them? Being civilized is all fine and good, but being free is much better.
Probably had a lot to do with the fact that the sword required people to get "up close and personal" and could require great effort on the part of those weilding it.