The Jason Arday affair is beginning to remind me of Jussie Smollett.

Not because we know that Arday fabricated anything. We don’t. But because of the strange self-protecting logic that surrounds allegations of racism.

Smollett’s story was initially believed because it fitted so perfectly with what many people already believed about America: a black, gay actor attacked by racist, homophobic Trump supporters. The allegation seemed almost to validate itself.

Something similar is happening with Arday.

He says a severed pig’s head was sent to his family home. Yet police can reportedly find no record of the investigation he described. The butcher he said police visited says no officers ever came. There are apparently no photographs or contemporaneous messages.

He also says a masked man twice entered his Cambridge faculty building and threatened him, on one occasion with a knife. Yet the man was apparently captured by no CCTV, seen by no colleagues, and Arday reportedly warned nobody in the building at the time.

“To be honest with you, I thought you’d just believe me,” Arday told the Guardian. “Why would I lie?”

That sentence may be the most revealing part of the whole affair.

Because questioning Arday’s claims now risks being folded into the very narrative those claims are supposed to establish.

Arday says he has been targeted because of racism. Questions are raised about the evidence for his claims. Those questions are then portrayed as part of a “vile campaign” against him — which becomes further evidence that he is being targeted.

The allegation begins to protect itself.

He is a victim of racism, therefore questioning his account may itself be racist; and because questioning his account may be racist, his claim to be a victim of racism receives less scrutiny.

It is a perfect circle.

That is the lesson we should have learned from Jussie Smollett. When an allegation fits our view of the world perfectly, that is not a reason to scrutinise it less. It is a reason to scrutinise it more.

Claims of racism should be taken seriously. But no allegation should carry within itself an exemption from scrutiny.

Otherwise we have created a proposition that can never be falsified: believe the allegation and it is true; question the allegation and your questioning becomes further evidence that it is true.

When allegations of racism become a protective shield against legitimate scrutiny, they do a profound disservice to those who have genuinely suffered from racism. They don’t advance social justice. They make a mockery of it.