Personally, I don't think one needs to support the president or the war to support the soldiers, but this is a favorite talking point from the RNC.I'm unsure why this is such a confusing point. You can support the men and women who defend our country, who are asked to die so we can complain about morning traffic and overly hot coffee, without agreeing with the war or the President's policies.
The two are separate - think of it this way, do you blame Microsoft's programmers for the bugs or do you blame Microsoft? You can the utmost respect for an employee of Microsoft without having that same feeling toward the company.
It's no different with our troops. You can support their service, no matter where they are told to go, and still disagree with why they are there.