The left and right don't understand each other's conceptions of morality, and don't even try to do so. This is the message I take from last night's row about Laurie Penny's reaction to the vandalism of a war memorial.

Laurie said:

What's disgusting is that some people are more worried about a war memorial than the destruction of the welfare state.

"Destruction" isn't entirely hyperbole. The Tories' proposed £12bn cut in welfare spending is equivalent to £45 per week per working age benefit recipient. That would impose horrible hardship upon many.

Instead, Laurie's mistake consists in doing exactly what Jonathan Haidt in The Righteous Mind accused the left of: she's seeing morality as comprising just one idea whereas the right sees others.

Haidt and his colleagues claim that there are (at least) five foundations of morality: care/harm, fairness/cheating, loyalty/betrayal, authority/subversion and sanctity/degradation. The left, he says, stresses the first two of these but underweights the last three.

And this is just what Laurie was doing. She was emphasizing the care principle, whilst being blind to the sanctity principle - to the idea that we believe that some things, such as vandalizing war memorials, are wrong because they break taboos even if they don't do material harm to anyone.

Now, there is, of course, a ton of hypocrisy surrounding ideas of sanctity. Many of those on the right who were outraged by the vandalism tell Muslims to tolerate cartoons of Mohammed and mock the left's preoccupation with political correctness and "safe spaces." And the left is sometimes deliberately transgressive of some norms whilst outraged by others: compare reactions to Richard Dawkins and Katie Hopkins. What's sacred and taboo to some is just nonsense to others.

Which brings me to the problem. Far too many - on left and right - are so wrapped up in their own narcissism and so quick to condemn others that they fail to understand (or even try to) where others are coming from: the virtue of Haidt's framework is that it facilitates such understanding.

What's being lost in all this is Mill's classical liberal idea - that there is a strong case for cognitive diversity. For me, Laurie's voice is a welcome contributor to this diversity. If the herdthink that rushes to condemn leads to her being more inhibited, something valuable will be lost.