From his article "What You Can't Say (2004):
The statements that make people mad are the ones they worry might be believed.
I suspect the statements that make people maddest are those they worry might be true.
"In every period of history, there seem to have been labels that got applied to statements to shoot them down before anyone had a chance to ask if they were true or not.
"Blasphemy", "sacrilege", and "heresy" were such labels for a good part of western history, as in more recent times "indecent", "improper", and "unamerican" have been."
"I think many interesting heretical thoughts are already mostly formed in our minds.
If we turn off our self-censorship temporarily, those will be the first to emerge."
Oh, and I really like that one:"I suspect the biggest source of moral taboos will turn out to be power struggles in which one side only barely has the upper hand. That's where you'll find a group powerful enough to enforce taboos, but weak enough to need them."
"To do good work you need a brain that can go anywhere.
And you especially need a brain that's in the habit of going where it's not supposed to."
"Training yourself to think unthinkable thoughts has advantages beyond the thoughts themselves. It's like stretching. When you stretch before running, you put your body into positions much more extreme than any it will assume during the run. If you can think things so outside the box that they'd make people's hair stand on end, you'll have no trouble with the small trips outside the box that people call innovative."
"The people you can say heretical things to without getting jumped on are also the most interesting to know."
"When people are bad at math, they know it, because they get the wrong answers on tests.
But when people are bad at open-mindedness they don't know it.
In fact they tend to think the opposite."