How is someone having a certain controller preference affecting anyone but themselves? If what they use is "bad" and "not as good as THIS controller option" stop telling them it's bad and to use something else. If I was you I would take advantage of it and beat the stuff out of them in smash if their controller option is apparently terrible.
In all seriousness, what they choose to play Smash with in no way affects you, and if they like it, they have every right to use it. They're not an idiot for having preferences.