It doesn't make sense, you know π
Maybe off topic but related question, does Mister Sinister immune to the Cavalier EQ Magik boss's reverse control SPs?
As others have pointed out, he has never been immune to reverse controls themselves. However, his helmet provides immunity to the reverse controls specifically triggered by Emma Frost's telepathy (a nod to the intention of the helmet, which is to block psychics from the mind of the wearer). Reverse controls from a node, however, are not psychic attacks from an opponent, and thus do not allow Magneto to bypass them.
Better question is why take magneto against Magik anyways ? Umm. Any bleed champ will do against her