Never ascribe to an opponent motives meaner than your own. J M Barrie
The art of politics consists in knowing precisely when it is necessary to hit an opponent slightly below the belt. Konrad Adenauer
There are exceptions to all rules, but it seldom answers to follow the advice of an opponent. Benjamin Disraeli
The leader of genius must have the ability to make different opponents appear as if they belong to one category. Adolf Hitler
The opposition is indispensable. A good statesman, like any other sensible human being, always learns more from his opponents than from his fervent supporters. Walter Lippmann
There is an ancient saying, which is a true one – ‘To fight against two opponents is a difficult thing’. Plato