Oh really? After Slick Willie, flipping the bird would be considered small potatoes to our media friends. Kerry already been caught saying the F word to a large group of people which is about the most vulgar thing a candidate can say and is certainly worse than flipping off someone. And the F word was on his web site and then removed.
I don't think anything short of indictment for murder could bring down Kerry or keep dems from rallying around him like some union boss.
Two critical differences between the Slick Willie thing and such a photo:
1) For those who do not take the time to know what is going on (including swing voters), photos have much more impact then words.
2) Swing voters tend to be more turned off a scandal in the context of firing a sitting President rather then evaluating a candidate for President.
The dims will vote for the rats no matter what, the reasonable and well informed will vote for the pubbies. But, the perception of the largely ignorant swing voter makes the difference.