Why should I support the troops?
For purposes of thought-experiment, imagine if our military were made up entirely of mercenaries. Would we pin "support Blackwater" magnets on our cars? Why not? Because they're just in it for the money, of course. They don't care about "duty, honor, country", whatever that may mean. They have a baser motive.
The Troops, though, are another story. They are, according to popular mythology, all patriotic Good Samaritans, intent on dedicating their lives to defending this Great Country and Spreading Democracy to the less enlightened corners of the world.