Why Gates would be hard to fire

From Kausfiles:

On Warren Olney's To the Point, LAT veteran Doyle McManus says Robert Gates

is in the unusual position of not being a cabinet member who can't really be fired because if the president and the secretary of defense were to end up at loggerheads on an issue, that could be politically very damaging to the president. [E.A.]

This seems astonishingly wrong. Obama can fire Gates more easily because Gates is a Bush holdover, no? Obama won an election by opposing Bush's policies. ..

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But .... isn't Gates hard to fire not because of political factors, but because he's widely recognized as being ... how shall I say it ... competent?

And it doesn't matter what Obama ran on. (Kennedy won on a "missile gap" that didn't exist.) He has to govern on what is, not what turns on the left. And Gates at least stands for successful policies. (Which are also Bush policies.)

Gates might be hard to fire because, for Obama to succeed as prez, he might have to listen to Gates.