I think the quote was from Secretary Forrestal. The sentiment didnt last that long though because they did have to raise hell in Congress after WWII to avoid chopping block.
I think the USMC offers a unique mix of skill sets under one branch.
http://en.wikipedia.org/wiki/Marine_Air-Ground_Task_ForceThey are still much more deployable and nimble than the Army but you are correct though that some of the less kinetic actions simply did not call for the USMC. A lot of missions in Iraq called for Army MP's but we were there so long that they had to be rotated in into a role they werent best equipped for. Im admittedly a dilettante in the field though so Ill leave it at that for now.