The award winning author Walter Mosley once said: “A man’s bookcase will tell you everything you’ll ever need to know about him.” How very sexist of him.

For, as Jessica Valenti has rightly pointed out in the Guardian, sexism isn’t just about the big stuff – “outrageous, explicit misogyny – domestic violence, sexual assault and attacks on reproductive rights, to name a few,” it’s also about the small stuff.

Mr Mosley, a woman’s bookcase will also tell you everything to know about her.

Valenti has been thinking about this, and has come to the realisation that it is our every-day choices which single us out as sexists (and presumably as racists). Who we read, what we tweet, what we re-tweet. Welcome to the cutting edge of feminism.

“Passive bias is still bias – and it has ripple effects into the broader culture. Is it really so much to ask that we pay attention to what shapes our tastes?” she asks.

To illustrate her point, Valenti cites two examples. The first, a man seated next to her on the underground who was scrolling through Twitter. At first glance he seemed to share her interests. “I was tickled to be sitting next to a like-minded person.” But then, despair loomed large. Valenti twigged that he was only following men. “He was following fantastic and smart men, but still – as far as I could tell, all men.”

The second example given is of a writer Valenti admires who took part in a podcast. “He spoke eloquently about his passions and mentors – and the people whose work he liked most. All men.” Uh oh.

If we are to rid society of the evils of sexism and racism, we must all take a look inside ourselves and resolve to do better, Valenti helpful intones.

“Like it or not, your taste in music, books, television or art says something about you: it sends a message about what you think is worth your time, what you think is interesting and who you think is smart. So if the only culture you pay attention to is created by men, or created by white people, you are making an explicit statement about who and what is important.”

Helpfully, she suggests ways in which we can resolve to be better people. We could follow the example of Anil Dash, who last year decided to only re-tweet women, after realising that he was retweeting men three times as often as he was retweeting women.

“This, despite my knowing how underrepresented women’s voices are in the areas I obsess over, such as technology and policy and culture. I could do better.” Dash said.

“We all could,” adds Valenti.

Here endeth the progressive sermon of the day.