How to "deal" with casuals? There's not much of an issue, I think.
I mean, if it's just getting annoyed by new players spamming attacks and whatnot, I wouldn't take that seriously. You don't really "deal" with that.
When it comes to bringing them in to the community, then there are various ways. As I recall another post mentioning, don't go easy on 'em when you're battling them. You really do learn well when you see how much you suck.
It wouldn't hurt to lend a helping hand, too. Take a friend of mine, for example. I've mentioned to him my interest about competitive Smash a couple of times, yet he keeps thinking he can kick my butt with Link. So, what do I do?
Smash him into the ground and make fun of him!
Well, minus the teasing. It really doesn't hurt to slowly teach those that are unfamiliar with techniques and whatnot afterwards. Guide them through terminology. Teach them tournament standards. Help them with their character -- anything! After I beat him a couple of times, I taught him a few general tricks, and in no time, I kept getting bombarded with projectiles when trying to recover from the ledge. I guess he just learns fast, but basically, give those who want to become a part of the community a boost -- especially if they usually play casually. I must say that I'm not very involved in the community at all, but I really intend on somehow helping those new Smash players get into the tourney-play scene, whether by video or whatever.
Try not to be a douche to them, either. We already have a bad image from some people that don't play the game seriously. There's no need to further the stereotype, ya'know?