The idea that Magneto wasn't leaving Charles to his death in X2 is absurd.
While Magneto does have respect for Charles (as opposing generals might) Charles was still in opposition to Magneto's methods and ultimate goals. If Magneto could limit or outright remove Charles, he'll do it for the advancement of his goals.
In X2, Charles was stuck in an illusion by mutant 143 to 'find the humans' and kill them all through Cerebro. Magneto taps his fingers on Charles wheelchair, says "Goodbye Charles," and leaves him in a room he can't physically get out of and an illusion he can't get out of-143 will just try try again and he already succeeded anyways.
Nothing on film translated into Magneto giving Charles a means to escape: there was no amount of time given where all the humans would die and Cerebro made 'useless' and Charles stopping what he's doing, no mention that 143 would stop his illusion making and that Charles would get out of it, Magneto's tone of voice and gesture did not foretell his survival-it was a goodbye, and Magneto closed the frickin' door on him.
Magneto left Charles in a situation that would have led to his death-physically and mentally incapacitiated for all intents and purposes.