There is one particular type of bad argument that has always existed, but it has now spread like tar over the world-wide web, and is seeping into the pubs, coffee shops and opinion columns everywhere. It is known as 'what-aboutery' - and there was a particularly ripe example of it in response to one of my articles last week.

As a rhetorical trick, it is simple. Anyone can do it, and we are all tempted sometimes. When you have lost an argument - when you can't justify your case, and it is crumbling in your hands - you snap back: "But what about x?"

Download the new Independent Premium app Sharing the full story, not just the headlines

You then raise a totally different subject, and try to get everybody to focus on it - hoping it will distract attention from your own deflated case.

So whenever I report on, say, atrocities committed by Israel, I am bombarded with e-mails saying: "But what about the bad things done by Muslims? Why do you never talk about them?" Whenever I report on the atrocities committed by Islamists, I am bombarded with e-mails saying: "But what about Israel? Why do you never write about the terrible things they do?" And so it goes on, whatever the subject, in an endless international shifting of blame, united in the cry: "What about them! Talk about them instead!"

This argument is almost always disingenuous. How do I know? Because when you write back and explain that, why, I do actually criticize Islamists/Israel/the US/China/whoever-you-have-picked-out-randomly, and here are the articles where I do it, nobody ever writes back and says: fair enough; you consistently condemn human rights abuses, no matter who commits them. No. They scrape around for another "what about." What about Tibet? What about Sri Lanka? What about North Korea? This list never ends, as the other side tries to draw your attention further and further from what you were discussing.

Independent readers have just seen a classic example. Last week I reported from Dubai, pointing out that this glittering city was built on what Human Rights Watch calls "slavery" - bitterly poor people who are conned into going there and forced to stay by a medieval dictatorship. Amongst others, I interviewed an Emirati man called Sultan al-Qassemi who passionately defended this system, saying that it is absolutely right that these workers are blasted with water cannons, arrested, and deported if they try to strike against their slavery-style conditions.

He did not react to my article by responding to the many criticisms I made of Dubai. He can't. He knows they are true. Instead he wrote a piece for the Independent asking: But what about Britain? He listed many things wrong with Britain - homelessness, detention without trial, the abuse of trafficked workers - and cried: talk about them instead!

As it happens, I have criticized all these things about Britain myself, in the British press, and in publications across the world. The difference is - Sultan doesn't oppose the appalling things about his own country. He cheers them on - and all he can do to distract from this shameful fact is to try to change the subject.

The best way to respond to what-aboutery is to state a simple truth. Say it slowly: there can be more than one bad thing in the world. You can oppose American atrocities, and Chinese atrocities. You can be critical of Israel, and of Islamism. You can condemn Dubai's system of slavery, and the fact people are detained without trial in Britain. You can stand independent of governments - including your own - and criticize anyone who chooses to abuse human rights. The world is not divided into a Block of Light, and a Block of Darkness; you don't have to pick a tribe and defend its every action.

So whenever you hear the cry "But what about…!", you can reply: what about we ignore this crude attempt to change the subject, and focus on the subject in hand?