Stupid people! Thinking of setting up a Facebook group dedicated to an inflammatory cause? Why not simply scream your views into an empty breadbin instead? All the cathartic release, none of the lingering opprobrium.

One of the chief joys of the internet is the way it has liberated millions of anonymous hecklers, strikingly few of whom had hitherto risked sharing their coruscating views in public because people tended to yawn, or ask them to shut up, or physically attack them. Suddenly they had an outlet, and before long, a vastly inflated sense of self-worth. They could pop up, courageously tell a blogger that she was fat, and disappear into the night like Raffles the gentleman thief.

If I was designing the comments section for a website, I'd insist that every posting be accompanied by the poster's full name and portrait – unless they preferred to remain nameless, in which case their username, by default, would be Timid McSqueaky, and their comments would appear in weak yellow text on a bright white background, like urine in the snow. (Inevitably, there would be complaints that some commenters required anonymity because they were whistleblowers, dissidents or victims of some kind. Fair enough: they'd be able to submit their comments via a moderator.)

Of course, most activity on Facebook is accompanied by the user's full name and portrait, something the members of the Facebook group 'RIP RAOUL MOAT YOU LEGEND' failed to consider fully. It's offensive on many levels, not least because anyone who refers to any public figure other than King Arthur as a "legend" really ought to be denied access to food, water or any kind of comfortable horizontal surface for a minimum of 96 hours.

Mind you, if the ensuing interviews are anything to go by, the group's creator, Siobhan O'Dowd, can scarcely be blamed for failing to consider the consequences of her actions, because she doesn't seem to possess any power of thought whatsoever, and comes across a bit like a tree trunk that's recently learned to grunt in response to nearby sounds. Rather than labelling her a SICKO in bold type on the front cover, the tabloids really ought to run the story on their 33rd page under the heading THICKIE DOES THICK THING.

Attempting to blame Facebook seems especially short-sighted: equally dumb and inflammatory statements are made in the Have Your Say sections of newspaper websites every day. Occasionally the readers even manage to out-spite the columnists themselves. Furthermore, an inflammatory Facebook group is established every two seconds, although since the majority tend to consist of outraged overreactions to palpably false tabloid fantasies about Muslim groups demanding the execution of Mr Kipling and suchlike, we don't tend to hear much about them, even though they contain far more threatening hate speech than the pro-Moat page could muster. O'Dowd's group was chiefly unusual in going against the tabloid grain.

Not that she's adopting an intellectual position, of course. Her idea of "adopting an intellectual position" probably means not standing on all fours. On YouTube there's a recording of a radio interview in which a TalkSport presenter runs so many rings around her, it's a wonder he didn't black out from the centrifugal force. In the end he exposes and exploits her stupidity so mercilessly, I found myself experiencing pangs of sympathy for her.

Which puts me on wobbly territory, because it turns out I've been getting the concept of sympathy wrong all these years. I thought it referred to a sense of compassionate understanding that could be applied in varying degrees to an infinite number of individuals. Now, thanks to David Cameron, I realise it's an all-or-nothing, binary state of mind. You either have sympathy, or you don't, and in this instance Cameron claims he can't understand people who show any sympathy whatsoever for Moat. "It is absolutely clear that Raoul Moat was a callous murderer, full stop, end of story," he said. "There should be sympathy for his victims; there should be no sympathy for him."

He rejected the idea of censoring idiots on Facebook, but the worrying implication of his position on sympathy is the notion that it's an either/or choice: a finite substance, rather than a basic human trait. But you can't simply switch it off. Torturers and dictators aside, there are very few people it's impossible to feel absolutely zero sympathy for.

If I had to assign a quantifiable figure to my sympathy, which I guess I should since the prime minister has instructed me on how best to apportion it, I reckon I feel 100% sympathy for the victims and 1% sympathy for Raoul Moat: he receives a solitary crumb of pity, doled out on the basis that he suffered a gigantic mental collapse which led him to commit a series of pathetic and unforgivable deeds before killing himself.

That gives us a total of 101% sympathy. A sympathetic overspend. A deficit of compassion. Maybe that kind of extravagance can't be maintained in our current age of austerity. After all, we have to make cuts somewhere. What was it John Major said? "Society should condemn a little more and understand a little less"? Or to boil that down to a tabloid strapline: MORE JUDGMENT, LESS THOUGHT.