As an airman from 1996-2000 I can tell you personally that this almost caused me to lose my mind (not being able to trash-talk Clinton) during his last term in office. There were a lot of clenched teeth and boiling tempers everywhere I went about this forced reverence for the Commander-in-Chief.
Last week I was up in Killeen, Texas, Home of Fort Hood and saw lots of Ron Paul and Obama bumper stickers and not one single McCain sticker.
Not a scientific sample, but it did surprise me.