"If evolution theory is true, why does the story keep changing? First Charles Darwin proposes his theory of evolution, then Stephen Jay Gould tries to shore up some gaping holes in it by proposing his theory of "punctuated equilibrium": a totally discredited band-aid solution to the insolvable problems with evolution theory which all responsible scientists are now trying to distance themselves from. If you look at the way evolutionists squirm about with constantly-changing arguments, it's quite obvious that evolution is a theory in crisis, and they just won't admit it."

This is a particularly clever piece of rhetorical trickery: it takes advantage of the fact that scientists, being reasonable people, are constantly tweaking their theories in order to improve them as new evidence comes to light.

Creationists, on the other hand, have been peddling the same story for more than a thousand years, and it is guaranteed never to change no matter what evidence is produced. Which approach sounds more reasonable to you?

Science, like technology, is in a constant state of improvement. No one would look at (for example) automotive technology and say that the carburetor didn't work because it was superseded by fuel injection, so why do people look at Darwin's theory of evolution and conclude that it was wrong because improvements were eventually made to it?

And yes, Stephen Jay Gould's theory of punctuated equilibrium is an improvement (or more accurately, an addition) to Darwin's original theory. Contrary to creationist claims, it has not been dismissed, and in fact, one would be hard-pressed to consider the history of violent or catastrophic events in the planet's history (such as massive volcano eruptions or asteroid impacts) and not conclude that there must be periodic events which cause major upheavals, hence changes in the rate of evolution.

Fallacy watch:

• Ad-hominem (the argument "you changed your mind therefore you're wrong" is a form of the "attack the messenger rather than the message" fallacy)
  
• Outright lie (technically not a logic fallacy, but it is simply an outright lie that evolution theory is in crisis or that Gould's theory of punctuated equilibrium has been discarded).