Some dishonest tricks in arguments
Today I saw this vivid example of extending the opponent's argument:
A public speaker ... between the wars maintained that a country with as much distress as there was then in Great Britain could not afford heavy expenditure on expensive luxuries, giving as an example the field sports of the rich. This was a moderate and reasonable proposition. One of his hearers accused him afterwards of inconsistency in attacking all expenditure on what were not necessities, since, presumably, the speaker had recreations of his own on which he expended money.
The speaker refused to have his proposition extended and reasserted his original statement that not all expenditure on recreation was undesirable, but that excessive expenditure was, pointing out that he had already shown that this was his view by arguing that some amount of luxury expenditure of this kind was desirable for everybody. His opponent now said: "To be logically consistent, you ought to disapprove of all luxury expenditure if you disapprove of expenditure on grouse moors and deer forests". To this unreasonable assertion I know of no satisfactory reply except to deny that there is any such logical necessity. The statement that "Some Xs are Y" is as logically adequate as "All Xs are Y", and is indeed more likely to be true.
Source: Robert Thouless, Straight and Crooked Thinking
The books also contains examples of diversions, irrelevant objections, slogans, and other tricks.
On page 84, there is this description of what is left out from a description of even the most widely accepted values:
A predigested thought formula expressed in a form of words which is handed from one person to another may be called a 'slogan'. A successful slogan may possess great power in influencing the behaviour of a large number of people in one direction. No complicated statement of the doctrines of Rousseau could have been as effective in directing the French Revolution as the slogan "Liberty, fraternity, equality".
Now, this slogan is obviously predigested. It is a very simple statement which would need a complicated expansion to mean anything exactly. Such an expansion of 'liberty' would need to explain what the people were and what they were not to be free to do; of 'fraternity', to explain with whom they were to be fraternal (not aristocrats or enemies of their country); of 'equality', in what respects they were to be equal.
The world would truly be a saner place if this "argument" was vaporized. The book summarizes it as:
the argument that we should not make efforts against X which is admittedly evil because there is a worse evil Y against which our efforts should be directed.
Thouless recommends that we can deal with this by "pointing out that this is a reason for making efforts to abolish Y, but no reason for not also making efforts to get rid of X." This is a rational defense, but I wish there was something better one could say.