Giant Death Robot, is just an affectionately named "Mech", The reason they wen't with the title Giant Death Robot is a testament to the developers love of thier modding community, by grasping this totally fun concept into the future tech stage of the game, its not silly, (apart from the name) A Space Elevator can't be built yet, though we will be able to build one eventually, yet the technology was in Civ4BTS, no one complains about that, so why complain about a mech, we have mechs that exist today, and for combat purposes or soon will be, not Giant Death Robots mind you, but thats a possibility for the future of war fare.
I just think its funny how the developers take a suggestion from the modding community, (atleast the name sake) and implement it into the game, and some people find it outrageous. Perhaps you shouldn't be participating here if you don't want developers to look at your idea's ^>^.