Diane Abbott didn't even use all of her 140 characters, but she still managed to provoke a backlash that speaks volumes. After tweeting, in an exchange with Bim Adewunmi about the political implications of the "black community", Abbott commented that "White people love playing 'divide & rule' We should not play their game #tacticasoldascolonialism".

Twitter is a poor medium for reflecting on the complex history and contemporary structures of race. Abbott captures a central political fact, which is that white people in western societies have benefited from their histories of colonial exploitation. This does not make people equally culpable for it, and in unequal, exploitative societies, it clearly doesn't imply comparable benefit. But racism does confer degrees of relative privilege in states where whiteness continues to be regarded as the norm.

For those who consistently call for a "grown-up conversation" about race, there should be much to debate here. However, yesterday's outrage illustrated that such debates are mainly opportunities to enforce the compensatory victimhood of "reverse racism". In the Telegraph, Toby Young consulted his dictionary, and found Abbott's remark to be the very definition of racism. After many hours of tweeting and ratcheting up media coverage, blogger Harry Cole appeared on Sky News to lament those who "use race as a political tool".

The insistence on an apology evinces a new standard of racial sensitivity among rightwing commentators. Racist jokes are always "taken too seriously", but Abbott's sentence is offensive, no contextualisation allowed. Minorities "cry racism" on a whim, but endless coverage of a digital blip is serious political commentary. Anti-racism is "victimology", but white people are victims of reverse racism. And once the rehearsal of outraged equivalence is in gear, anything goes. Cole noted that the unfortunate proximity of Abbott's tweet to the Stephen Lawrence convictions demonstrated how "racism works both ways", illustrating Richard Seymour's contention that as the verdict "drew attention to institutional … racism in British society, it was a dead cert that the media would search for a way to restore white victimhood".

Beyond the opportunistic timing, this discourse of victimisation demonstrates why racism does not work both ways. Bias, stereotyping and violence are human actions, but racism is not a synonym for individual prejudice. Instead, racism is the systemic discrimination of whole groups of people cast as outsiders, deemed incapable of full incorporation into society, and treated with suspicion on this basis. It has a deep and lasting effect on individuals' life chances and consequent wellbeing, and is damaging to the social fabric as a whole. For all the equivalences drawn between clumsy and prejudicial references to skin colour, racism is inherently political; it requires the power to contribute to racial oppression.

The right's response to an insistence on history, structure and power is to launch a faux attack on "paternalism": "Are you saying that black people are incapable of racism?" Yet this exasperated common sense is distilled from a long history of backlash politics, one that recognises that it is precisely because of the legacy and persistence of racism that its political force, and the experience of it, must be undermined.

The recognition of racism's existence is always accompanied by its denial. It is often forgotten that Enoch Powell's infamous "rivers of blood" speech was made in opposition to the passage of the first Race Relations Act in 1968. Recognition and redress of racism – not the fact of immigration – would lead to "the black man [having] the whip hand over the white man".

Rewriting racism as a human impulse elides it as a process born of a set of specific historical contexts, such as the conquering of the Americas, the birth of slavery, and modern colonialism. In the post civil-rights era US, and the UK of postcolonial immigration, it has become a strategic political imperative to regard "reverse racism" not only as a fact of life, but to cast "race relations" as a zero-sum game where any modest redress of historical injustice and discrimination inevitably entails "unfairness to whites". This not only denies the experiences of those who face racism, but also makes solidarity with those exploited on the basis of class, and discriminated in terms of gender and sexuality more difficult. In a zero-sum game, a focus on racism can be cast as deflecting attention from other struggles.

In extremis, this strategy contends that if racism does exist, it is now the preserve of minorities using "liberal multiculturalism" to get revenge on a cowed white majority. In the US, shock-jock Rush Limbaugh presented the election of Barack Obama as evidence that whites are becoming "'the new oppressed minority' [with] Republicans… going along with it by 'moving to the back of the bus and obliging by drinking only out of designated water fountains'."

In France, the spokesperson of the anti-racist Mouvement des indigenes de la République, Houria Bouteldja, is being prosecuted for "anti-French racism" by the General Alliance Against Racism and for the Respect of French and Christian Identity (AGRIF), an outfit with historical roots in the Vichy regime and the OAS in Algeria. In a 2007 radio discussion, Bouteldja used the term souchien, riffing on the expression Français de souche, coined by National Front leader Jean-Marie Le Pen in 1979 to refer to "indigenous" (white) French people. Nouveau philosopher Alain Finkielkraut, chose to add a hyphen to render the word as sous-chien, or "sub-dog" (mongrel), and accused Bouteldja of anti-French or anti-white racism. This paved the way for a prosecution based, as Raphael Confiant argues, on contesting the "right of French people of non-European origin … to make puns like any other French person".

And that is the point. False, ahistorical equivalences are designed to further double standards. The media storms brewed to condemn Abbott's tweet or Bouteldja's pun as "racist" are based on an implicit understanding; a true reckoning with racism would, at minimum, diminish the power and privilege that allows elite actors to play the victim.

• Follow Comment is free on Twitter @commentisfree