This was a slip of the tongue and should be given a pass. Bush has done the same thing, too many times. Reasonable people accept these as a simple mistake, unreasonable people don't (democrats).
I'd agree with you except for the singular fact Kerry likes to take BOTH sides of the issue without considering how absurd it sounds. Sometimes he REALLY takes both sides at the same time, just to play it safe.
But really, the point is that Kerry WILL be given a pass -- c'mon! we know what he MEANT to say! It's no big deal! It just proves he's human!
When Bush makes a gaffe, it's front page news. Often for more than one day. Why? Well, it just proves that Bush is a moron!