Red hair and yellow eyes; the defining characteristics of the Gerudo. I like how you call that silly when it's based on evidence, then connect Ghirahim to Dark Link based on nothing at all.
Nintendo should sell a clock like this.
What about the Dark Skin? Saying a single person is the origin of an entire race doesn't make sense to me.
Girahim turns into a dark Master Sword, how the hell is that nothing at all? It was the first thing I thought of when he turned into it.
Plus, Ghirahim clearly ends up hating Link and the two (three if you count four swords) times he appears he pretty much appears just to fight him, there's doesn't even seem to be a connection to Ganondorf although this is just speculation
EDIT: He also shows up in ST and OoA. Maybe in TP, but that's not exactly it.
Seriously.