Was it this one?
Though it might have been this one. (In fact I think this really might be the one you’re thinking of).
If either of them aren’t the one you’re looking for, please let me know (I didn’t re-listen to them, I simply popped the links in because I think I remembered him talking about that in these, but it’s been awhile since I listened to them. I know, I know; if I was really “hardcore” I’d have all the Tom Woods videos on a playlist running an endless loop as I sleep, but I’m not that “pro”).
It’s also possible in his “Libertarian Speech I Would Give to the Whole Country.”
[Edit: Oh, wait, it is quite possibly Applying Economics to American History, which punctures a series of “myths.”]