Given the movies are their own alternate universe, that version of Juggernaut IS a mutant. It's like complaining that Beast Wars Scorponok is wrong because he's not a Headmaster.
Isn't it a can of Nebulan?Oh, now that's just a whole other can of worms!
Well, Juggy and Magneto worked together in "Pryde of the X-Men".Juggernaut shouldn’t be a mutant or working for Magneto in the first place.