I don't have anything against a nail gun - I own a couple including a staple gun. The reason I don't use it in fine furniture is that I don't like the nail holes showing - no matter how you fill them, to me, they still show. But anywhere else, including places on fine furniture that won't show, I'll use them. I especially use them for quick things around the shop - jigs and stuff like that.
I'm pragmatic - and I think our woodworking ancestors were also. Use what will get the job done and produce the final results you are looking for.
Mike
Go into the world and do well. But more importantly, go into the world and do good.