The President, more than any other individual, sets the national debate. So when the President makes a mind boggling dumb speech invoking Vietnam in support of his Iraq adventure, he renders the entire nation dumber.
As Kevin Drum says:
Another longtime conservative fantasy makes its way out of the fever swamps and into the public discourse, where we'll all be expected to stroke our chins and pretend to take it seriously for the next week or so.
We can't ignore these lunatic ravings, because they aren't coming from that guy with crazy eyes down on the corner. They are coming from the President of the United States. These ideas gain credence just because the President has said them. Add making us dumber to the long list of damages that Bush has inflicted on the Country.