What is objectionable, what is dangerous, about extremists is not that they are extreme, but that they are intolerant. The evil is not what they say about their cause, but what they say about their opponents. – Robert Francis Kennedy

Intolerance of ambiguity is the mark of an authoritarian personality. – Theodor Wiesengrund Adorno

Nothing dies so hard, or rallies so often as intolerance. – Henry Ward Beecher

Tolerance is a very dull virtue. It is boring. Unlike love, it has always had a bad press. It is negative. It merely means putting up with people, being able to stand things. – E. M. Forster