The reason there are so many different fallacies is because there have been so many people stupid enough to make them, among them well-respected philosophers.

Descartes even has one named after him, the Cartesian Circle, basically a circular argument or 'begging the question'. He did this in reworking St Anselm's Ontological Argument for the Existence of God which runs as follows:

(1) God is a being better than which cannot be conceived
(2) What's better, a God that exists or one that doesn't? One that does of course, so
(Conclusion) God Must Exist.

Perhaps the same argument can be applied to prove the existence of the Perfect Pizza?

Aristotle on the other hand defines moral worth or goodness as fulfilling ones role as a rational human. So why is it good to fulfil ones role as a rational human? Because fulfilling ones role as a rational human is good.

There are many other good fallacies. The Man in the Mask fallacy for example (another one old Des is guilty of). "I know what my father looks like, I do not know what the man in the mask looks like, therefore my father is not the man in the mask". The Appeal to Force is funny ("agree with me or I'll hit you") and apparently counts as a logical fallacy. Tell them that next time you get mugged.