Yesterday, a minute or so before 3pm, with a policeman struggling for his life outside, and with details of what had gone on still sketchy and confused, the work of parliament was suspended. David Lidington, leader of the House of Commons, rose to explain why the lockdown was necessary. And his Labour opposite number, Valerie Vaz, replied that “Our thoughts and prayers are with the police officer”, a sentiment with which Lidington concurred and with which the house murmured its agreement.

I wandered over and unlocked the church, putting up a board to invite passersby to come in and light a candle or say a prayer. You can see Big Ben from some parts of my parish and the church was filled with the sound of helicopters overhead and police sirens whizzing past. A handful of people dropped by over the couple of hours I sat there. Not many, I know, but it was still worth opening up. It was my way of showing respect. Of expressing solidarity. Of managing my own anxiety. This church was bombed by the Nazis on the first day of the blitz. It has seen great violence. And it has been calmly rebuilt. It symbolises the defiance of Londoners in the face of terror. This felt the right place to be. And as I sat quietly, I kept up with unfolding events via Twitter. And that was my mistake.

“Can everyone stop all this #PrayforLondon nonsense. It’s these bloody stupid beliefs that help create this violence in the first place,” tweeted Julia Hartley-Brewer, a middle-England talk radio host in the mould of Katie Hopkins. Now there is a time and a place for atheists to have a pop about whether prayer is a waste of time. Even for a debate about the role of Islam in the formation of terrorism. Bring it on. But bundling together the person who had just come into church to pray for the dying policeman with the policeman’s very attacker was gratuitously offensive and just plain ignorant.

But the charmless Hartley-Brewer was having none of those who challenged her: “So having an opinion on religious expressions is indecent now? Have you thought of joining Isis?” she preposterously spat back. Of course, she hardly matters. But all over Twitter, in millions of micro-encounters, all this surround-sound unpleasantness builds up and gradually eats away at our civility. Under that flag of convenience called free speech, people tear up their decency in the search for “likes”. Oh, how cheaply we trade the things that matter most. Have social media and the stamping foot of the 24-hour news cycle killed off the quiet dignity of grief, both religious and non-religious?

Some things, often the most important things, do not lend themselves to immediate comment. Bigger thoughts take time and silence, and require waiting for the right perspective. Yes, I know, defending slowness and silence in a newspaper is a bit like defending chastity in a brothel. But the world does not readily give up its truth just because you click on a webpage or react to a tweet. “You must wear your eyes out, as others their knees,” said the great Welsh poet RS Thomas.

Prayer is not a way of telling God the things he already knows. Nor is it some act of collective lobbying, whereby the almighty is encouraged to see the world from your perspective if you screw up your face really hard and wish it so. Forget Christopher Robin at the end of the bed. Prayer is mostly about emptying your head waiting for stuff to become clear. There is no secret formula. And holding people in your prayers is not wishful thinking. It’s a sort of compassionate concentration, where someone is deliberately thought about in the presence of the widest imaginable perspective – like giving them a mental cradling.

But above all, prayer is often just a jolly good excuse to shut up for a while and think. The adrenaline that comes from shock does not make for clear thinking or considered judgment. Those who rush to outrage say the stupidest things.