VPAF aircraft were only responsible for a fraction of those aircraft downed, he doesn't bother to point that out.......
I think indirectly, he did point it out by mentioning the 6,000 AAA sites that "accounted for more than 65% of our combat losses," and 9,000 SAMs. [ I see as I send this, A4s has kindly already mentioned this.

)
Nevertheless, our kill ratio in the early years was atrocious against the very limited VPAF; which led to the Ault report and subsequently, the establishment of TOPGUN - the effects of which were immediate and well documented, and lasted for decades.
Still, the air-to-air war was mostly a side-story. For years, the North was off limits; and the MiGs never ventured South. CAS was the name of the game. And when the North finally did open up again, we still had immediate air-superiority… but with even larger losses. The MiG's were mostly harassment rather than a factor - although they bagged some good men. The major losses – and they were heavy - came from primarily AAA. And at the very end of the war, during Linebacker II, while Mig's downed two only AF F-4's then, it was SAMs (old, antiquated SA-2's) that downed 15 B-52's along with a number of other AF and Navy tacair.
Training, usually by necessity, concentrates upon a single type of threat and canned tactics in a sterile, simulated environment. This tends to give one tunnel vision. But actual war is multi-faceted, replete with many changing, dynamic threats and always some big - no, make that huge - surprises. You can never really know what you will face, until you actually face it in enemy skies. Then reassess, and quickly readjust - because the enemy will too.
Not to quibble with HJ, but Hanoi's skies, as bad as they were, may have very much been preferable than the "Estonia mentioned." At least Hanoi's heavy and concentrated defenses had less-than-state-of-the-art, Russia hand-me-downs.

(also, SAM sites were indeed legit targets for us, and desirable; it was the pervasive, red-boxed no-bomb-zones where Jane Fonda's entourage was on that particular day where we couln't bomb.)