Part of the difference is Rowling still holds so much cultural weight (somehow). So many people still know and watch and purchase Harry Potter stuff. Seinfeld only really holds that weight amongst older conservatives. He’s only popular amongst the people perpetuating the hate. Rowling’s stuff is popular amongst those who should know better. I do agree we should boycott more (I personally do boycott a fair bit), but comparing the current impact of Rowling to the current impact of Seinfeld is crazy.