I have a confession to make: I have spent money in Starbucks. Not every day, but yes, on occasion I have ventured into the temple of mediocre coffee and smooth jazz and emerged with my politics intact. According to Louise Mensch, Theresa May and tedious hordes of free market apologists, this is impossible. The second one sickly drop of cinnamon latte passes your lips, you forfeit your right to comment upon the abuses of capitalism. Like Persephone in the underworld, who ate the food of the dead and was forced to live amongst them, you are doomed to remain a silent drone in a corporate wasteland, forever regretting your moment of caffeine-deprived weakness.

We have been hearing versions of this argument ever since protest became a regular feature of contemporary politics. The notion peddled by right-wing commentators is that you cannot have any serious, sustained objections to fiscal feudalism and its discontents if you happen to have grown up in a detached house, or attended an elite university, or if you once, in a moment of weakness late at night, found yourself walking out of a well-known conglomerate with a box of suspicious chicken pieces coated in unmentionable sauce and wondering what your life had become. Anyone who engages left-wing politics in a serious way faces this idiotic charge. I've lost count of the number of times I've been told that because I have a smartphone and went to a private school, I have no business speaking about social justice.

At root, this argument is about a fear of ideology: a terror of real political and economic alternatives in a society that would still rather group people into warring tribes based on income and lifestyle. The left is not entirely immune from this sort of lazy reasoning. It is, of course, indicative that the vast majority of the British cabinet are millionaires, but even if they all lived together in a skip in Southend, it would hardly make their permissive stance on corporate tax avoidance morally tenable.

The trouble with that logic is that it cuts both ways. There are plenty of decent, politically right-on people who believe that buying an overpriced macchiato, or a pair of shoes they don't need, or whatever it is that alleviates, for a moment, the numbing exhaustion of daily life in a post-Fordist society in some way excludes them from the debate. A guilty little smile of complicity accompanies this thought process, as they hand over money at the cash register. We've had our imperialist latte, it says, so we're already fifth columnists, it says -- there's nothing we can do to make a difference, much as we'd like to.

I, for one, am sick of that excuse. If capitalism is a disease, everything and everyone is infected. Look around the room you're in and tell me with absolute certainty that there's nothing in it that was stitched by child-slaves in the developing world, or sold to you by exploited workers from the kind of company that thinks "sick pay" is the name of a minor 90s grunge band. There is almost no way to exist in this society without being contaminated by capitalism, unless you spend your whole life lying down in the dark, in a recycled rattan coffin, being drip-fed organic vegan mulch by a succession of fairly paid assistants, and if you do, I'm sure you'll feel great about yourself, but people will still make fun of you, and you won't be a step closer to changing the world.

Quarantining yourself from capitalism is not going to create a cure, and those who mock protesters and radicals for owning iPhones and buying burgers know that extremely well. Left, right and vacillating in the middle, we all need to decide if there is still room in this age of austerity for ideas and ideals, or if we truly want a world where we're just lined up into suspicious rival camps according to how much we earn. American libertarians call that sort of thuggish, annihilating excuse for politics "class war". Class warriors call it "missing the point".