The Philosophical Society offers a plethora of logical fallacies that might add some spice to your sermons! Here is one for the lessons on the Gerasene demoniac and the swine.
The Gadarene Swine Fallacy – The GSF is the fallacy of supposing that because a group is in the right formation, it is necessarily on the right course; and conversely, of supposing that because an individual has strayed from the group and isn’t in formation, that he is off course. The individual may seem lost to the group but not off course to an ideal observer.
From R.D. Laing’s Politics of Experience. Here is an excerpt:
The ‘off course’ criterion is the ontological. One needs to make two judgements along these different parameters. In particular, it is of fundamental importance not to confuse the person who may be ‘out of formation’ by telling him he is ‘off course’ if he is not. It is of fundamental importance not to make the positivist mistake of assuming that, because a group are ‘in formation,’ this means they are necessarily ‘on course.’ This is the Gadarene swine fallacy.