Across numerous allegiances (Swift fans, Kanye fans, Britney Spears fans, Trump fans, Hillary fans), there are people sitting behind keyboards who will say terrible things. Saying "in this specific instance, no one would ever, ever do this" is overreaching. Anonymous Internet commenters will say all sorts of things. I don't know Taylor's friend, but I'd believe anyone who said "I got death threats" for saying something controversial.