Agreed. I didn't mean to imply that Space Marines are going anywhere; there are some tasks that only Space Marines, and occasionally only Terminators, can handle.
As a completely unrelated aside, I do occasionally find it weird how the Imperium is taught to feel a way, but then a blatant reverse happens with someone important, and that exception is allowed. In some ways, anyway, I view the Space Marines as mutants; they are Humans who have been dramatically changed into something more. Under most circumstances, the Imperial mantra is "suffer not the mutant", but because these mutants were created by the Emperor, they are perfectly fine (minus a few fools who maybe do view Space Marines negatively, but don't dare say so). The Emperor is my other example. Humans HATE psykers, no matter how critical to the Imperium a select variety might be, and the really powerful ones are feared and burned, yet the Emperor, the most powerful psyker on record, is loved and adored; no one ever feared that His power might backfire, and place Khorne physically in front of everyone.
In both cases, I know that there is established stuff to cushion these into being acceptable, but it still seems odd for a group who reviles "different", but worships a super-psyker sorcerer (shamans kind of seem to use "magic") and his army of mutant supermen. Two blazing examples of being as far from baseline Human as possible, yet revered by those who seek to stagnate Human development and progress.