In spring 2012, a week after setting up a website to catalogue experiences of gender inequality, I asked Lady Gaga for her support via Twitter. Keen to raise awareness of my newly created Everyday Sexism Project, I hoped she might spread the word among her millions of followers.

The next morning, I sleepily reached for my phone and saw more than 200 new notifications. I clicked eagerly on the first message and stopped cold. It wasn’t, as I had hoped, the first of many new entries from women who had suffered harassment or assault. It was a brutally graphic rape threat – and the moment I became aware of the sheer force of hatred that greets women who speak out about sexism.

The threats continued to flood in. The sheer tenacity was startling. Who were these men, who could spend days, weeks – years, even – bombarding a woman they had never met with detailed descriptions of how they would torture her?

Over time, things became clearer. I met men who opposed feminism in different settings, and began to recognise their varied tactics. In some ways, the online abusers – who hurled hatred from behind a screen – were the least threatening. The repetition in their arguments (if you can call “get off your high horse and change your tampon” an argument) made it clear that their fury was regurgitated: rooted in a fear of that man-hating, society-destroying “feminazi” of online forum fantasy.

More sinister were the slick, intelligent naysayers who hid in plain sight. Men who scoffed at social events, confidently assuring those around us that sexism in the UK was a thing of the past and I should look to other countries to find “real problems”. Men who asked my husband, in commiserating tones, how he coped with being married to me. Politicians who told me I was “unnecessarily negative” and that girls these days didn’t know how lucky they were. The newspaper picture editor who overlooked the content of my interview when he announced his priority was to make me look “as sexy as possible”. People with the power to change things and the will to keep them exactly the same.

Despite this, the site was a success, and over the next five years, hundreds of thousands of testimonies flooded in. Almost every woman or girl I met told me their story, too. A nine-year old who had received a “dick pic”. An elderly lady who had been assaulted by her late husband’s best friend. A young black woman refused entry to a nightclub while her white girlfriends were waved through. A woman in a wheelchair who was told she would be lucky to be raped. My assumptions about the type of person who suffers particular forms of abuse and the separation between different kinds of prejudice quickly shattered.

The sadness of the stories was a heavy thing to bear, as was the continued abuse I received. A man who had offered me directions crossed the street in disgust when I told him I was on my way to give a talk about workplace sexual harassment, snapping: “For God’s sake, we’ve got to have some fun!” An interviewer asked me live on air whether it was difficult having no friends because I was so humourless. An American commentator wrote a blog publicly warning my husband he would one day come home to find I had burned down our house, murdered our children and joined a “coven of lesbian witches”. Somewhere around the time I received a death threat alongside the claim I was a dripping poison that should be eradicated from the world, I started seeing a counsellor. And – at low moments – I seriously considered the coven.

Another joy was being part of a burgeoning wave of feminism, standing alongside others tackling everything from media sexism to female genital mutilation. Perhaps the most important lesson I learned was how closely connected the different forms of inequality are. It is vital to resist those who mock and criticise us for tackling “minor” manifestations of prejudice, because these are the things that normalise and ingrain the treatment of women as second-class citizens, opening the door for everything else, from workplace discrimination to sexual violence.

To be a feminist, I have learned, is to be accused of oversensitivity, hysteria and crying wolf. But in the face of the abuse the project uncovered, the sheer strength, ingenuity and humour of women shone like a beacon. The dancer who performed for hours on the tube to reclaim the space where she was assaulted. The woman who waited five years to present her contract and a salt cellar to the careers adviser who had told her he would eat her paperwork if she ever became an engineer. The pedestrian who calmly removed the ladder of a catcalling builder, leaving him stranded on a roof.

That’s why I can honestly say that the experiences and lessons of the past five years have left me more hopeful than despairing. I can’t celebrate this milestone, exactly, representing as it does a collective outpouring of grief, anger and trauma. But I think of the resilience, the solidarity, the resistance, and I can’t mourn it either. In five years, I have learned that the problem is immense, but the will to fight it is greater still.

The Guardian, Monday 17 April 2017