I hate Facebook as much as the next person, but prior to this week I had no intention of boycotting it. The gesture would, I told myself, be both meaningless and totally unrealistic. I have never successfully given up a single bad habit – bacon, Milky Ways, leaving the dishes in the sink overnight – so why would the urge to check Facebook work out any different?

And in bald outline, the Cambridge Analytica story wasn’t enough of an impetus to change. After the news broke, most people I know, while tutting and fretting over how awful it all was, also believed themselves to be entirely immune to the effects of propaganda and ad targeting. For idiot racists, data harvesting is a prelude to mind control; for the rest of us it’s an abstract political problem.

Or at least it was until this week. I have occasionally had sympathy for people who create something that becomes much bigger than anticipated and then have to scramble to explain what they’ve done. (I always thought Simon Cowell was a stark example of this, someone who, while no doubt appalling in lots of ways, was made to answer too widely for bad taste in primetime TV).

If I had given Mark Zuckerberg much thought before now, I would probably have put him in a similar category, as someone I considered with vague distaste but no real animosity. Then several things happened in rapid succession to recategorise Facebook in my mind from a simple bad habit – in which the onus was on me, the addict, to seek help or move on – to something else: an entity whose sole purpose is to take the piss out of its users.

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It was a piece in the New York Times last week that articulated this fact more clearly than I have seen elsewhere and in a way that finally drove the point home: we, as Facebook users, are not the company’s customers but the company’s product.

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The other lightbulb moment came courtesy of Zuckerberg’s appearance before the Senate committee, which not only provided a handy and highly personalised visual on which to hang one’s dislike – the bland face, the android expression, the cult-like choice of Facebook-blue tie – but also offered cast-iron proof of the company’s bad faith.

It was Lindsey Graham, the Republican senator for South Carolina, who finally flushed out the disingenuousness at the heart of Facebook’s utopian mission statement. Graham invited Zuckerberg to remember an internal memo that circulated at Facebook in 2016 in which the author, Andrew Bosworth, a vice-president of the company who once taught Zuckerberg at Harvard, jocularly noted that while maybe Facebook “costs a life by exposing someone to bullies” or “maybe someone dies in a terrorist attack coordinated on our tools”, hey-ho, “anything that allows us to connect more people more often is de facto good”.

No action was taken against Bosworth, and even though Zuck assured the senators he didn’t agree with the memo’s statement, he also added, in a winsome aside: “Boz is what we call him internally.” For some reason it was the chummy cuteness of “Boz” that put the final nail in the coffin. That’s it, I’m done; 24 hours clean and it feels tremendous.

• Emma Brockes is a Guardian columnist