In addition to what Don posted I think its instructive to know the Right's distain for Kerry predates the rise of Bush by decades. The derision traces back to Kerry's Vietnam Era testimony before Congress (1971) where he charged U.S. Military war atrocities as the norm and aligned himself with the Winter Solider Investigation (1972). Kerry's stance was(is) taken as agenda ridden, disingenuous, and contributing to a domestic hostility toward the war that would ultimately lead to defeat.
But atrocities as described were the norm , it was a very messy conflict .
What ultimately led to defeat is almost identical to the current conflict , domestic hostility is only one aspect of it .