It's a standard debating technique. Your opponent offers a counter-argument. You respond with a smile, saying, "You make my point for me." It often works but only rarely is it completely true. One of those rare occasions has arisen right here on Comment is Free – via the thread below Mehdi Hasan's valedictory piece for this site.

Mehdi's parting shot focused on the abuse he and other prominent Muslims regularly endure when they enter the public square, with insults often hurled via the medium of the online comment. Sure enough, many of those who disagreed with Hasan's essay piled on to the discussion below the line to use language and imagery so vile it instantly confirmed the very case he had been making.

Islam "is not a religion worth protecting. I would welcome its extinction," wrote one. Another, preferring to play the man rather than the ball, declared, "You ARE a shit-head." And there were lots more, often dressed up in pseudo-intellectual language, branding Islam backward or denouncing its beliefs and practices as "odious," and culminating in an ultimatum by which Islam's, and therefore Muslims', place in Britain was deemed conditional on adaptation to suit the critics' tastes: "If Islam is to be truly accepted as part of British society it must embrace science. It must embrace rationality, sexuality and reason."

You don't have to accept every word Mehdi Hasan has written to be troubled by this. He and I would, for example, part company on one figure he cites, namely Lord Ahmed – who has an awkward record of inviting known antisemites to the House of Lords. Nor can I deny that I, like others, felt uneasy at some of the language he used a few years back, when he appeared to describe non-Muslims as "people of no intelligence" and as "cattle." But I find pretty plausible his explanation of that and, to his credit, he himself conceded that his "phraseology was ill-advised and inappropriate."

You can dislike Mehdi's views on these and other grounds as much as you like and still be appalled at the treatment he receives, apparently routinely. Even when he writes on a subject that has no connection to Islam, he is still attacked in lurid, anti-Muslim terms. As Hasan recalls: "A recent interview of mine with the shadow chancellor, Ed Balls, elicited the following response: 'Get out of my country, goatfucker.'"

We know what this is and we should call it by its name: it is racism, of the crudest kind. That last quotation is the easiest example, but the subtler ones are not much better. They can be confusing, because they often dress up in progressive, Guardian-friendly garb – slamming Islam as oppressive of gay and women's rights, for example – but the thick layer of bigotry is visible all the same. Call it progressives' prejudice.

Mehdi's article names me among the journalists who have stood against the tide of anti-Muslim bigotry. If I've earned my place in that group, here's why. Each time I come across the kind of abuse he cites I mentally replace the word "Islam" with "Judaism" and "Muslim" with "Jew". I know how I would feel if I was bombarded with long screeds denouncing Jewish faith and customs as sinister, alien, backward or bonkers, just as I know how I would feel if I were told Jews need to change their ways if they are to be accepted into polite society.

Not that this requires a huge leap of the imagination. I'm afraid that I and other Jewish writers have had more than a taste of the treatment Mehdi describes, if not at quite the same regularity or volume. And I recognise his lament that the tiniest thing can set off the haters. The Guardian ran a light Short Cuts item recently about a botched bit of Hebrew translation that had made it into the US-UK television comedy Episodes. The second commenter on the thread took the opportunity to denounce Jewish dietary laws.

I've also grown used to a variant of that progressives' prejudice, by which "card-carrying liberal lefties", as Mehdi calls them, in their rush to defend Palestinian rights end up banging out the old, nasty tunes about the Jews.

So yes, I'm glad to stand with Mehdi Hasan, even when we don't see eye to eye. And if you want to disagree with me below the line, go ahead. But take care – you might end up making my point for me.

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