The young men who murdered an off-duty soldier in Woolwich, in South East London, on 22 May seem to have been Islamists - supporters of violently reactionary theocratic politics. We condemn the killing.
For the most part, the threat posed by Islamists - whether ultras like these ones, or softer varieties - is not directed against off-duty soldiers. It is directed against women, LGBT people, atheists and secularists, dissidents and critical-minded people in Muslim-majority countries and in some Muslim communities in countries like Britain.
Islamism is a threat to the working class, in the first instance the Muslim working class. But this killing has ramped up other more powerful threats too.
There is a nationalist, racist, far right backlash under way, championed by the English Defence League, which will violently target not only Muslims - there have already been attacks on mosques - but many other dark-skinned people living in Britain.
The far right campaign feeds off and feeds into a more widespread, "mainstream" hysteria about Muslims and terrorism, playing on the ridiculous and disgusting idea that all or most Muslims are in some way responsible for the actions of the Islamist killers. This in turn interacts with a media promoting sensationalist messages about the threat of terrorism. (Tellingly, the murder - also by brutal stabbing - of an elderly Muslim man, Mohammed Saleem, it seems by a white racist, in Birmingham on 29 April has generated much less and very different coverage.)
It also seems there will be an authoritarian state backlash which will target civil liberties and democratic rights in the name of fighting terrorism.
The left needs to stand strong against all this, speaking up for rational thought in the midst of hysteria, advocating working-class unity, defending Muslim communities and helping organise anti-racist counter-protests against the likes of the EDL.
This is, or should be, a wake up call for the labour movement and socialists. If we cannot build a political force in working-class communities capable of appealing to the angry and dispossessed, then reactionary ideas like radical Islamism and nationalist racism will continue to spread.