I have been an active twitter user since 2009 ish and met my then friend through twitter. we met up in real life and everything was great until she discovered tumbler.
I washy fully aware of everything going on (I'm a carer so mind was on other things) but noticed changes in her. She spent more and more time on tumblr than twitter. I remember showing her terfisaslur.com and she just said along the lines of this 'well terfs are nasty and there was this thing lesbians said about the cotton ceiling and they were just being c*nts' that was around 2015 ish.
So i dug in some more and asked her questions about it because I was very much clueless at the time. I remember asking her about sexual orientations and why would a male who has transitioned claim to be a lesbian etc when thats just not true. She told me I was wrong even after I pointed out that sexual orientation is based on sex not identity and recording sexual orientation incorrectly means that sexual health resources wouldn't be channeled to the right groups. Lesbians are at lower risk of infections and some cancers. she agreed but told me I was wrong again.
I then went back with a US clinic leaflet that described the vagina as a front hole and asked about it. I remember telling her that if anyone has to rename body parts to stop distress then its a major mental health condition. She told me again I was wrong but didn't explain why.
she brought up sexual orientation again about her trans friend. Female but transitioned to male and how them saying they were a heterosexual male made the world 'better'.
I questioned and pointed out the kind of disassociation with ones body is often a sign of mental distress and serious trauma. She confessed the trans friend had been raped by a man despite saying they were a lesbian and suffered other sexual violence. I pointed out that perhaps her friend really needed help to deal with complex trauma not a cocktail of medicines that won't treat the underlying causes.
She ranted at me that apparently trans people offend me. (they dont) It was her complete inability to debate or question this stance - when we have debated and disagreed and questioned everything from our differing views on politics, feminism, sexism, the best foods to eat (and the worst) and ways to deal with everyday issues.
Tumblr radicalised her. Turned her from an average person dealing with life to very nervous person who believed they were autistic, non binary, with complex trauma, an eating disorder, depression etc and trying a myriad of unhealthy ways to fix all of the above despite never seeing a doctor for any of them. The only thing I agree with is the eating disorder, she developed a very unhealthy relationship with food probably down to the increasing number of 'clean eating' blogs she was reblogging and sharing. the number of labels that followed over the 2-3 years she was on tumblr (still is I believe) changed her in so many damaging ways. The person I knew is a very very different person now.
Mumsnet radicalised me but these ladies here understood my concerns and actually offered the time to debate and disagree with me, educate me and help me figure out my position when my friend refused. For her it was this is right or we aren't friends.
she 'broke up' with me via a tumblr blog.