I think the difference between Viet Nam and the war to defend against radical Islam is this:
The Viet Nam era "anti-war" and MSM crowd wanted their Ho in Hanoi to win. (Post war comments by NV general Giap praised the American press as his "most valuable guerrilla.")
No one in today's "anti-war" and MSM crowd (I hope) wants radical Islam to win. They do want, as Ellen Ratner put it, Bush to "mess up."
Of course a "mess up" would mean a larger number of U.S. casualties -- but as a letter published in the S.F. Chronicle put it, the losses would be worth it to get rid of Bush.
The "anti-war" and MSM crowd sees domestic political advantages for them but also, just as important IMO, they want the U.S. to have to crawl to an international group and hand over responsibility and our military to it to fight the war.
One thing is the same however, "Bring it all down, man" is the objective.
I just love how they want Bush out of office. I don't suppose they've given even a minutes thought to the fact that if they were, by some strange quirk of fate, to succeed that Cheney would then become president.