This is allegedly a quote from George Bernard Shaw. The idea is that they are dangerous because they no longer care about the world, having their eyes fixed on Eternity. Therefore, they are capable of all kinds of mischief.
In his own old age, Shaw must have hoped that he was still as dangerous to the smug ruling classes as he had been all his life. Shaw cared about the world passionately until his last breath – like other exceptional men such as Churchill and de Gaulle. It comes with being great.
Shaw must have been thinking about other old men. He was right. In their dotage they can indeed be dangerous. Especially to themselves, like King Lear.
Stephen Harper certainly agrees with Shaw. In his proposal for Senate reform, he suggests a nine-year term limit. That in addition to the existing age limit of seventy-five. Since he knows most senators over seventy-five are neither great nor in their dotage he must think they are dangerous.
Even if they are Conservative.